diff --git a/Packages/ICCeryCore/Sources/ICCeryCore/CGATS/CGATSParser.swift b/Packages/ICCeryCore/Sources/ICCeryCore/CGATS/CGATSParser.swift
index 327603a..8b0fc25 100644
--- a/Packages/ICCeryCore/Sources/ICCeryCore/CGATS/CGATSParser.swift
+++ b/Packages/ICCeryCore/Sources/ICCeryCore/CGATS/CGATSParser.swift
@@ -73,7 +73,7 @@ public enum CGATSParser {
         _ contents: String,
         sourceURL: URL? = nil
     ) throws -> CGATSDataset {
-        guard !contents.isEmpty else { throw .emptyFile }
+        guard !contents.isEmpty else { throw CGATSParseError.emptyFile }
 
         let ext = sourceURL?.pathExtension.lowercased() ?? ""
         let isCSV = ext == "csv" || contents.trimmingCharacters(in: .whitespacesAndNewlines)
@@ -101,10 +101,10 @@ public enum CGATSParser {
         }
 
         guard let formatStart, let formatEnd, formatEnd > formatStart + 1 else {
-            throw .missingBeginDataFormat
+            throw CGATSParseError.missingBeginDataFormat
         }
         guard let dataStart, let dataEnd, dataEnd > dataStart + 1 else {
-            throw .missingBeginData
+            throw CGATSParseError.missingBeginData
         }
 
         let rawFieldNames = splitFields(lines[formatStart + 1])
@@ -139,7 +139,7 @@ public enum CGATSParser {
             let lineIndex = dataStart + offset
             let rawRow = splitFields(lines[lineIndex])
             guard rawRow.count == fieldNames.count else {
-                throw .incorrectArity(line: lineIndex + 1, expected: fieldNames.count, got: rawRow.count)
+                throw CGATSParseError.incorrectArity(line: lineIndex + 1, expected: fieldNames.count, got: rawRow.count)
             }
 
             var sample = RawSample(id: String(offset), lineIndex: lineIndex)
@@ -153,7 +153,7 @@ public enum CGATSParser {
                             groupMax[group, default: 0] = max(groupMax[group, default: 0], number)
                         }
                     } else if !cleaned.isEmpty {
-                        throw .nonNumericValue(field: name, value: raw, line: lineIndex + 1)
+                        throw CGATSParseError.nonNumericValue(field: name, value: raw, line: lineIndex + 1)
                     }
                 } else {
                     sample.strings[name] = raw
@@ -239,7 +239,7 @@ public enum CGATSParser {
             lines.append(line)
         }
 
-        guard !lines.isEmpty else { throw .emptyFile }
+        guard !lines.isEmpty else { throw CGATSParseError.emptyFile }
 
         // Wrap a bare CSV / ISO28178 file in the canonical CGATS block
         // structure so the boundary-based parser below can handle it.
diff --git a/Tests/ICCeryCoreTests/AppPathsTests.swift b/Tests/ICCeryCoreTests/AppPathsTests.swift
index 2316056..130e0d8 100644
--- a/Tests/ICCeryCoreTests/AppPathsTests.swift
+++ b/Tests/ICCeryCoreTests/AppPathsTests.swift
@@ -1,27 +1,25 @@
-import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 
-@Suite("AppPaths")
-struct AppPathsTests {
-    @Test func appDataDirUsesBundleID() {
-        #expect(AppPaths.appDataDir.path.contains("Library/Application Support/com.gronod.iccery2"))
+final class AppPathsTests: XCTestCase {
+    func testAppDataDirUsesBundleID() {
+        XCTAssertTrue(AppPaths.appDataDir.path.contains("Library/Application Support/com.gronod.iccery2"))
     }
 
-    @Test func logFileIsUnderLibraryLogs() {
-        #expect(AppPaths.logFile.lastPathComponent == "iccery.log")
-        #expect(AppPaths.logFile.path.contains("Library/Logs/com.gronod.iccery2"))
+    func testLogFileIsUnderLibraryLogs() {
+        XCTAssertEqual(AppPaths.logFile.lastPathComponent, "iccery.log")
+        XCTAssertTrue(AppPaths.logFile.path.contains("Library/Logs/com.gronod.iccery2"))
     }
 
-    @Test func bundledArgyllDirIsInsideResources() {
-        #expect(AppPaths.bundledArgyllDir.lastPathComponent == "Argyll")
+    func testBundledArgyllDirIsInsideResources() {
+        XCTAssertEqual(AppPaths.bundledArgyllDir.lastPathComponent, "Argyll")
     }
 }
 
-@Suite("WizardStage")
-struct WizardStageTests {
-    @Test func stepperOrderIsOneThroughFive() {
-        #expect(WizardStage.stepperStages.map(\.stepperIndex) == [1, 2, 3, 4, 5])
-        #expect(WizardStage.calibrate.stepperIndex == nil)
+final class WizardStageTests: XCTestCase {
+    func testStepperOrderIsOneThroughFive() {
+        XCTAssertEqual(WizardStage.stepperStages.map(\.stepperIndex), [1, 2, 3, 4, 5])
+        XCTAssertNil(WizardStage.calibrate.stepperIndex)
     }
 }
diff --git a/Tests/ICCeryCoreTests/ApplycalArgsTests.swift b/Tests/ICCeryCoreTests/ApplycalArgsTests.swift
index fb10001..b4cb09f 100644
--- a/Tests/ICCeryCoreTests/ApplycalArgsTests.swift
+++ b/Tests/ICCeryCoreTests/ApplycalArgsTests.swift
@@ -1,22 +1,19 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("ApplycalArgs")
-struct ApplycalArgsTests {
+final class ApplycalArgsTests: XCTestCase {
 
-    @Test("Apply argv")
-    func applyArgv() throws {
+    func testApplyArgv() throws {
         let config = ApplycalConfig(
             calibrationPath: "/tmp/cal.cal",
             inputProfileURL: URL(fileURLWithPath: "/tmp/profile.icc")
         )
         let args = try ApplycalArgs.build(config: config)
-        #expect(args == ["-v", "-a", "/tmp/cal.cal", "/tmp/profile.icc"])
+        XCTAssertEqual(args, ["-v", "-a", "/tmp/cal.cal", "/tmp/profile.icc"])
     }
 
-    @Test("Unapply is emitted when the caller explicitly sets it")
-    func unapplyEmittedWhenConfigSet() throws {
+    func testUnapplyEmittedWhenConfigSet() throws {
         let config = ApplycalConfig(
             calibrationPath: "/tmp/cal.cal",
             inputProfileURL: URL(fileURLWithPath: "/tmp/profile.icc"),
@@ -25,6 +22,6 @@ struct ApplycalArgsTests {
         let args = try ApplycalArgs.build(config: config)
         // Builder emits -u only when the caller explicitly sets unapply.
         // The UI layer never passes unapply: true in v2.0.
-        #expect(args == ["-v", "-u", "/tmp/cal.cal", "/tmp/profile.icc"])
+        XCTAssertEqual(args, ["-v", "-u", "/tmp/cal.cal", "/tmp/profile.icc"])
     }
 }
diff --git a/Tests/ICCeryCoreTests/ArgsBuilderTests.swift b/Tests/ICCeryCoreTests/ArgsBuilderTests.swift
index 51e9605..05596c3 100644
--- a/Tests/ICCeryCoreTests/ArgsBuilderTests.swift
+++ b/Tests/ICCeryCoreTests/ArgsBuilderTests.swift
@@ -1,94 +1,80 @@
-import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 
-@Suite("ArgsBuilder")
-struct ArgsBuilderTests {
+final class ArgsBuilderTests: XCTestCase {
 
     // MARK: - option
 
-    @Test("option: nil emits nothing")
-    func optionNil() {
-        #expect(ArgsBuilder.option("-f", nil) == [])
+    func testOptionNil() {
+        XCTAssertEqual(ArgsBuilder.option("-f", nil), [])
     }
 
-    @Test("option: present value emits flag and value verbatim")
-    func optionPresent() {
-        #expect(ArgsBuilder.option("-f", "abc") == ["-f", "abc"])
-        #expect(ArgsBuilder.option("-f", "") == ["-f", ""])
-        #expect(ArgsBuilder.option("-f", "  padded  ") == ["-f", "  padded  "])
+    func testOptionPresent() {
+        XCTAssertEqual(ArgsBuilder.option("-f", "abc"), ["-f", "abc"])
+        XCTAssertEqual(ArgsBuilder.option("-f", ""), ["-f", ""])
+        XCTAssertEqual(ArgsBuilder.option("-f", "  padded  "), ["-f", "  padded  "])
     }
 
     // MARK: - optionIfNonEmpty
 
-    @Test("optionIfNonEmpty: nil and empty emit nothing")
-    func optionIfNonEmptyNilEmpty() {
-        #expect(ArgsBuilder.optionIfNonEmpty("-d", nil) == [])
-        #expect(ArgsBuilder.optionIfNonEmpty("-d", "") == [])
+    func testOptionIfNonEmptyNilEmpty() {
+        XCTAssertEqual(ArgsBuilder.optionIfNonEmpty("-d", nil), [])
+        XCTAssertEqual(ArgsBuilder.optionIfNonEmpty("-d", ""), [])
     }
 
-    @Test("optionIfNonEmpty: whitespace-only emits nothing")
-    func optionIfNonEmptyWhitespace() {
-        #expect(ArgsBuilder.optionIfNonEmpty("-d", "   ") == [])
-        #expect(ArgsBuilder.optionIfNonEmpty("-d", " \t\n ") == [])
+    func testOptionIfNonEmptyWhitespace() {
+        XCTAssertEqual(ArgsBuilder.optionIfNonEmpty("-d", "   "), [])
+        XCTAssertEqual(ArgsBuilder.optionIfNonEmpty("-d", " \t\n "), [])
     }
 
-    @Test("optionIfNonEmpty: trims surrounding whitespace")
-    func optionIfNonEmptyTrims() {
-        #expect(ArgsBuilder.optionIfNonEmpty("-d", "  label  ") == ["-d", "label"])
-        #expect(ArgsBuilder.optionIfNonEmpty("-d", "\tcal.cal\n") == ["-d", "cal.cal"])
+    func testOptionIfNonEmptyTrims() {
+        XCTAssertEqual(ArgsBuilder.optionIfNonEmpty("-d", "  label  "), ["-d", "label"])
+        XCTAssertEqual(ArgsBuilder.optionIfNonEmpty("-d", "\tcal.cal\n"), ["-d", "cal.cal"])
     }
 
     // MARK: - optionUnlessApprox
 
-    @Test("optionUnlessApprox: nil emits nothing")
-    func optionUnlessApproxNil() {
-        #expect(ArgsBuilder.optionUnlessApprox("-N", nil, skip: 0.50) == [])
+    func testOptionUnlessApproxNil() {
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-N", nil, skip: 0.50), [])
     }
 
-    @Test("optionUnlessApprox: exact skip value emits nothing")
-    func optionUnlessApproxExactSkip() {
-        #expect(ArgsBuilder.optionUnlessApprox("-N", 0.50, skip: 0.50) == [])
-        #expect(ArgsBuilder.optionUnlessApprox("-V", 1.0, skip: 1.0) == [])
+    func testOptionUnlessApproxExactSkip() {
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-N", 0.50, skip: 0.50), [])
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-V", 1.0, skip: 1.0), [])
     }
 
-    @Test("optionUnlessApprox: within epsilon emits nothing")
-    func optionUnlessApproxWithinEpsilon() {
-        #expect(ArgsBuilder.optionUnlessApprox("-N", 0.5005, skip: 0.50) == [])
-        #expect(ArgsBuilder.optionUnlessApprox("-V", 0.9995, skip: 1.0) == [])
+    func testOptionUnlessApproxWithinEpsilon() {
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-N", 0.5005, skip: 0.50), [])
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-V", 0.9995, skip: 1.0), [])
     }
 
-    @Test("optionUnlessApprox: outside epsilon emits flag")
-    func optionUnlessApproxOutsideEpsilon() {
-        #expect(ArgsBuilder.optionUnlessApprox("-N", 0.75, skip: 0.50) == ["-N", "0.75"])
-        #expect(ArgsBuilder.optionUnlessApprox("-V", 1.50, skip: 1.0) == ["-V", "1.50"])
-        #expect(ArgsBuilder.optionUnlessApprox("-N", 0.498, skip: 0.50) == ["-N", "0.50"])
+    func testOptionUnlessApproxOutsideEpsilon() {
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-N", 0.75, skip: 0.50), ["-N", "0.75"])
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-V", 1.50, skip: 1.0), ["-V", "1.50"])
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-N", 0.498, skip: 0.50), ["-N", "0.50"])
     }
 
-    @Test("optionUnlessApprox: POSIX formatting is locale-stable")
-    func optionUnlessApproxPOSIX() {
+    func testOptionUnlessApproxPOSIX() {
         // 1234.5 must never produce a grouping separator or comma decimal.
-        #expect(ArgsBuilder.optionUnlessApprox("-p", 1234.5, skip: 1.0) == ["-p", "1234.50"])
-        #expect(ArgsBuilder.optionUnlessApprox("-p", 2.0, skip: 1.0) == ["-p", "2.00"])
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-p", 1234.5, skip: 1.0), ["-p", "1234.50"])
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-p", 2.0, skip: 1.0), ["-p", "2.00"])
     }
 
-    @Test("optionUnlessApprox: custom epsilon and format honoured")
-    func optionUnlessApproxCustom() {
-        #expect(ArgsBuilder.optionUnlessApprox("-x", 1.005, skip: 1.0, epsilon: 0.01) == [])
-        #expect(ArgsBuilder.optionUnlessApprox("-x", 1.5, skip: 1.0, format: "%.1f") == ["-x", "1.5"])
+    func testOptionUnlessApproxCustom() {
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-x", 1.005, skip: 1.0, epsilon: 0.01), [])
+        XCTAssertEqual(ArgsBuilder.optionUnlessApprox("-x", 1.5, skip: 1.0, format: "%.1f"), ["-x", "1.5"])
     }
 
     // MARK: - flag
 
-    @Test("flag: true emits the bare flag")
-    func flagTrue() {
-        #expect(ArgsBuilder.flag("-G", when: true) == ["-G"])
-        #expect(ArgsBuilder.flag("-r", when: true) == ["-r"])
+    func testFlagTrue() {
+        XCTAssertEqual(ArgsBuilder.flag("-G", when: true), ["-G"])
+        XCTAssertEqual(ArgsBuilder.flag("-r", when: true), ["-r"])
     }
 
-    @Test("flag: false emits nothing")
-    func flagFalse() {
-        #expect(ArgsBuilder.flag("-G", when: false) == [])
-        #expect(ArgsBuilder.flag("-r", when: false) == [])
+    func testFlagFalse() {
+        XCTAssertEqual(ArgsBuilder.flag("-G", when: false), [])
+        XCTAssertEqual(ArgsBuilder.flag("-r", when: false), [])
     }
 }
diff --git a/Tests/ICCeryCoreTests/ArtefactFilesTests.swift b/Tests/ICCeryCoreTests/ArtefactFilesTests.swift
index aa85368..f5c7346 100644
--- a/Tests/ICCeryCoreTests/ArtefactFilesTests.swift
+++ b/Tests/ICCeryCoreTests/ArtefactFilesTests.swift
@@ -1,4 +1,4 @@
-import Testing
+import XCTest
 import Foundation
 import ImageIO
 import UniformTypeIdentifiers
@@ -10,9 +10,8 @@ private func tempURL(_ name: String) -> URL {
         .appendingPathComponent(name)
 }
 
-@Suite("Ti2Header")
-struct Ti2HeaderTests {
-    @Test func parsesKeywordsAndSibling() throws {
+final class Ti2HeaderTests: XCTestCase {
+    func testParsesKeywordsAndSibling() throws {
         let dir = FileManager.default.temporaryDirectory
             .appendingPathComponent("iccery-ti2-\(UUID().uuidString)")
         try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
@@ -31,18 +30,18 @@ struct Ti2HeaderTests {
         )
 
         let h = Ti2Header.parse(dir.appendingPathComponent("job.ti2"))
-        #expect(h.instrument == "i1iO")
-        #expect(h.patchCount == 800)
-        #expect(h.pageCount == 3)
-        #expect(h.hasSiblingTi1)
+        XCTAssertEqual(h.instrument, "i1iO")
+        XCTAssertEqual(h.patchCount, 800)
+        XCTAssertEqual(h.pageCount, 3)
+        XCTAssertTrue(h.hasSiblingTi1)
     }
 
-    @Test func missingFileYieldsEmptyHeader() {
+    func testMissingFileYieldsEmptyHeader() {
         let h = Ti2Header.parse(URL(fileURLWithPath: "/nonexistent/x.ti2"))
-        #expect(h.instrument == nil && h.patchCount == nil && !h.hasSiblingTi1)
+        XCTAssertTrue(h.instrument == nil && h.patchCount == nil && !h.hasSiblingTi1)
     }
 
-    @Test func numberOfFieldsIsNotPatchCount() throws {
+    func testNumberOfFieldsIsNotPatchCount() throws {
         let url = tempURL("t.ti2")
         try FileManager.default.createDirectory(
             at: url.deletingLastPathComponent(), withIntermediateDirectories: true
@@ -50,12 +49,11 @@ struct Ti2HeaderTests {
         try "NUMBER_OF_FIELDS 9\nNUMBER_OF_SETS 52\nBEGIN_DATA\n".write(
             to: url, atomically: true, encoding: .utf8
         )
-        #expect(Ti2Header.parse(url).patchCount == 52)
+        XCTAssertEqual(Ti2Header.parse(url).patchCount, 52)
     }
 }
 
-@Suite("TiffPreview")
-struct TiffPreviewTests {
+final class TiffPreviewTests: XCTestCase {
     /// Builds a real 2000×1000 TIFF in a temp dir via ImageIO.
     private func makeTiff(width: Int = 2000, height: Int = 1000) throws -> URL {
         let url = tempURL("big.tif")
@@ -81,50 +79,48 @@ struct TiffPreviewTests {
         return url
     }
 
-    @Test func producesCappedPNG() throws {
+    func testProducesCappedPNG() throws {
         let tiff = try makeTiff()
         let png = TiffPreview.previewPNG(tiff: tiff)
-        #expect(png != nil)
+        XCTAssertNotNil(png)
         // PNG magic
-        #expect(png!.prefix(8) == Data([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]))
+        XCTAssertEqual(png!.prefix(8), Data([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]))
         // Verify the cap by decoding the thumbnail header.
         let src = CGImageSourceCreateWithData(png! as CFData, nil)!
         let img = CGImageSourceCreateImageAtIndex(src, 0, nil)!
-        #expect(max(img.width, img.height) <= TiffPreview.maxEdge)
-        #expect(img.width == 1200)
+        XCTAssertTrue(max(img.width, img.height) <= TiffPreview.maxEdge)
+        XCTAssertEqual(img.width, 1200)
     }
 
-    @Test func nonTiffReturnsNil() throws {
+    func testNonTiffReturnsNil() throws {
         let url = tempURL("not-tiff.txt")
         try FileManager.default.createDirectory(
             at: url.deletingLastPathComponent(), withIntermediateDirectories: true
         )
         try "hello".write(to: url, atomically: true, encoding: .utf8)
-        #expect(TiffPreview.previewPNG(tiff: url) == nil)
+        XCTAssertNil(TiffPreview.previewPNG(tiff: url))
     }
 }
 
-@Suite("ArtefactFiles")
-struct ArtefactFilesTests {
-    @Test func base64RoundTrip() throws {
+final class ArtefactFilesTests: XCTestCase {
+    func testBase64RoundTrip() throws {
         let url = tempURL("a.txt")
         try FileManager.default.createDirectory(
             at: url.deletingLastPathComponent(), withIntermediateDirectories: true
         )
         try "hello".write(to: url, atomically: true, encoding: .utf8)
         let b64 = try ArtefactFiles.readBase64(url)
-        #expect(Data(base64Encoded: b64) == Data("hello".utf8))
+        XCTAssertEqual(Data(base64Encoded: b64), Data("hello".utf8))
     }
 
-    @Test func defaultWorkingDirExists() {
-        #expect(FileManager.default.fileExists(
+    func testDefaultWorkingDirExists() {
+        XCTAssertTrue(FileManager.default.fileExists(
             atPath: ArtefactFiles.defaultWorkingDirectory().path
         ))
     }
 }
 
-@Suite("ArtefactProbe profile resolve")
-struct ArtefactProbeProfileTests {
+final class ArtefactProbeProfileTests: XCTestCase {
     private func makeDir() throws -> URL {
         let dir = FileManager.default.temporaryDirectory
             .appendingPathComponent("probe-\(UUID().uuidString)")
@@ -134,93 +130,83 @@ struct ArtefactProbeProfileTests {
 
     // MARK: Basename probe matrix (#69)
 
-    @Test("basename probe: only .icc exists")
-    func onlyIcc() throws {
+    func testOnlyIcc() throws {
         let dir = try makeDir()
         let icc = dir.appendingPathComponent("job.icc")
         try Data("icc".utf8).write(to: icc)
-        #expect(ArtefactProbe.resolveProfile(basename: "job", cwd: dir)?.path == icc.path)
+        XCTAssertEqual(ArtefactProbe.resolveProfile(basename: "job", cwd: dir)?.path, icc.path)
     }
 
-    @Test("basename probe: only .icm exists")
-    func onlyIcm() throws {
+    func testOnlyIcm() throws {
         let dir = try makeDir()
         let icm = dir.appendingPathComponent("job.icm")
         try Data("icm".utf8).write(to: icm)
-        #expect(ArtefactProbe.resolveProfile(basename: "job", cwd: dir)?.path == icm.path)
+        XCTAssertEqual(ArtefactProbe.resolveProfile(basename: "job", cwd: dir)?.path, icm.path)
     }
 
-    @Test("basename probe prefers .icm")
-    func icmWins() throws {
+    func testIcmWins() throws {
         let dir = try makeDir()
         try Data("icc".utf8).write(to: dir.appendingPathComponent("job.icc"))
         let icm = dir.appendingPathComponent("job.icm")
         try Data("icm".utf8).write(to: icm)
         let url = ArtefactProbe.resolveProfile(basename: "job", cwd: dir)
-        #expect(url?.path == icm.path)
+        XCTAssertEqual(url?.path, icm.path)
     }
 
-    @Test("basename probe: neither exists returns nil")
-    func neitherExists() throws {
+    func testNeitherExists() throws {
         let dir = try makeDir()
-        #expect(ArtefactProbe.resolveProfile(basename: "job", cwd: dir) == nil)
+        XCTAssertNil(ArtefactProbe.resolveProfile(basename: "job", cwd: dir))
     }
 
     // MARK: Explicit URL matrix (#69 / #83)
 
-    @Test("explicit existing .icc wins even when .icm exists")
-    func explicitIccWins() throws {
+    func testExplicitIccWins() throws {
         let dir = try makeDir()
         let icc = dir.appendingPathComponent("job.icc")
         try Data("icc".utf8).write(to: icc)
         try Data("icm".utf8).write(to: dir.appendingPathComponent("job.icm"))
-        #expect(ArtefactProbe.resolveProfile(icc).path == icc.path)
+        XCTAssertEqual(ArtefactProbe.resolveProfile(icc).path, icc.path)
     }
 
-    @Test("explicit existing .icm wins even when .icc exists")
-    func explicitIcmWins() throws {
+    func testExplicitIcmWins() throws {
         let dir = try makeDir()
         try Data("icc".utf8).write(to: dir.appendingPathComponent("job.icc"))
         let icm = dir.appendingPathComponent("job.icm")
         try Data("icm".utf8).write(to: icm)
-        #expect(ArtefactProbe.resolveProfile(icm).path == icm.path)
+        XCTAssertEqual(ArtefactProbe.resolveProfile(icm).path, icm.path)
     }
 
-    @Test("explicit missing .icc flips to sibling .icm")
-    func flipExtension() throws {
+    func testFlipExtension() throws {
         let dir = try makeDir()
         let icc = dir.appendingPathComponent("job.icc")
         let icm = dir.appendingPathComponent("job.icm")
         try Data("icm".utf8).write(to: icm)
         let resolved = ArtefactProbe.resolveProfile(icc)
-        #expect(resolved.path == icm.path)
+        XCTAssertEqual(resolved.path, icm.path)
     }
 
-    @Test("explicit missing .icm flips to sibling .icc")
-    func flipToIcc() throws {
+    func testFlipToIcc() throws {
         let dir = try makeDir()
         let icc = dir.appendingPathComponent("job.icc")
         let icm = dir.appendingPathComponent("job.icm")
         try Data("icc".utf8).write(to: icc)
-        #expect(ArtefactProbe.resolveProfile(icm).path == icc.path)
+        XCTAssertEqual(ArtefactProbe.resolveProfile(icm).path, icc.path)
     }
 
-    @Test("explicit missing both returns the original URL")
-    func missingBoth() throws {
+    func testMissingBoth() throws {
         let dir = try makeDir()
         let icc = dir.appendingPathComponent("job.icc")
-        #expect(ArtefactProbe.resolveProfile(icc).path == icc.path)
+        XCTAssertEqual(ArtefactProbe.resolveProfile(icc).path, icc.path)
     }
 
-    @Test("unrelated extension is never rewritten")
-    func unrelatedExtension() throws {
+    func testUnrelatedExtension() throws {
         let dir = try makeDir()
         let mpp = dir.appendingPathComponent("job.mpp")
         let icc = dir.appendingPathComponent("job.icc")
         try Data("icc".utf8).write(to: icc)
         // Even though a sibling .icc exists, a missing .mpp stays .mpp.
-        #expect(ArtefactProbe.resolveProfile(mpp).path == mpp.path)
+        XCTAssertEqual(ArtefactProbe.resolveProfile(mpp).path, mpp.path)
         let txt = dir.appendingPathComponent("job.txt")
-        #expect(ArtefactProbe.resolveProfile(txt).path == txt.path)
+        XCTAssertEqual(ArtefactProbe.resolveProfile(txt).path, txt.path)
     }
 }
diff --git a/Tests/ICCeryCoreTests/BinaryResolverTests.swift b/Tests/ICCeryCoreTests/BinaryResolverTests.swift
index c1c7c76..06c1c5f 100644
--- a/Tests/ICCeryCoreTests/BinaryResolverTests.swift
+++ b/Tests/ICCeryCoreTests/BinaryResolverTests.swift
@@ -1,9 +1,8 @@
-import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 
-@Suite("BinaryResolver")
-struct BinaryResolverTests {
+final class BinaryResolverTests: XCTestCase {
 
     private func makeTree(_ body: (URL) throws -> Void) throws -> URL {
         let root = FileManager.default.temporaryDirectory
@@ -22,16 +21,16 @@ struct BinaryResolverTests {
         }
     }
 
-    @Test func overrideDirWinsWhenFileExists() throws {
+    func testOverrideDirWinsWhenFileExists() throws {
         let override = try makeTree { root in
             try touch(root.appendingPathComponent("targen"))
         }
         let bundled = try makeTree { _ in }
         let r = BinaryResolver(bundledRoot: bundled, overrideDir: override)
-        #expect(r.resolve("targen") == override.appendingPathComponent("targen"))
+        XCTAssertEqual(r.resolve("targen"), override.appendingPathComponent("targen"))
     }
 
-    @Test func overrideFallsThroughWhenMissing() throws {
+    func testOverrideFallsThroughWhenMissing() throws {
         let override = try makeTree { _ in }
         let bundled = try makeTree { root in
             let dir = root.appendingPathComponent("macos-universal")
@@ -39,10 +38,10 @@ struct BinaryResolverTests {
             try touch(dir.appendingPathComponent("instlist"))
         }
         let r = BinaryResolver(bundledRoot: bundled, overrideDir: override)
-        #expect(r.resolve("targen").path.contains("macos-universal/targen"))
+        XCTAssertTrue(r.resolve("targen").path.contains("macos-universal/targen"))
     }
 
-    @Test func universalPreferredWhenMarkerPresent() throws {
+    func testUniversalPreferredWhenMarkerPresent() throws {
         let bundled = try makeTree { root in
             for dir in ["macos-universal", "macos-x86_64"] {
                 let d = root.appendingPathComponent(dir)
@@ -51,10 +50,10 @@ struct BinaryResolverTests {
             }
         }
         let r = BinaryResolver(bundledRoot: bundled)
-        #expect(r.platformDir() == "macos-universal")
+        XCTAssertEqual(r.platformDir(), "macos-universal")
     }
 
-    @Test func fallsBackToArchDir() throws {
+    func testFallsBackToArchDir() throws {
         let bundled = try makeTree { root in
             let d = root.appendingPathComponent("macos-x86_64")
             try FileManager.default.createDirectory(at: d, withIntermediateDirectories: true)
@@ -64,20 +63,20 @@ struct BinaryResolverTests {
             bundledRoot: bundled,
             archDirs: ["macos-universal", "macos-x86_64"]
         )
-        #expect(r.platformDir() == "macos-x86_64")
+        XCTAssertEqual(r.platformDir(), "macos-x86_64")
     }
 
-    @Test func missingEverythingReturnsConstructedPath() throws {
+    func testMissingEverythingReturnsConstructedPath() throws {
         let bundled = try makeTree { _ in }
         let r = BinaryResolver(bundledRoot: bundled)
         // v1 semantic: path is returned; spawn surfaces the error.
-        #expect(r.resolve("targen").path.hasSuffix("macos-universal/targen"))
-        #expect(!r.exists(r.resolve("targen")))
+        XCTAssertTrue(r.resolve("targen").path.hasSuffix("macos-universal/targen"))
+        XCTAssertFalse(r.exists(r.resolve("targen")))
     }
 
-    @Test func mockAndGamutPaths() throws {
+    func testMockAndGamutPaths() throws {
         let r = BinaryResolver(bundledRoot: URL(fileURLWithPath: "/x"))
-        #expect(r.mock("chartread").path == "/x/mocks/chartread.mock")
-        #expect(r.referenceGamut("sRGB.gam").path == "/x/reference_gamuts/sRGB.gam")
+        XCTAssertEqual(r.mock("chartread").path, "/x/mocks/chartread.mock")
+        XCTAssertEqual(r.referenceGamut("sRGB.gam").path, "/x/reference_gamuts/sRGB.gam")
     }
 }
diff --git a/Tests/ICCeryCoreTests/CGATSParserTests.swift b/Tests/ICCeryCoreTests/CGATSParserTests.swift
index a5e9a74..8eb48d4 100644
--- a/Tests/ICCeryCoreTests/CGATSParserTests.swift
+++ b/Tests/ICCeryCoreTests/CGATSParserTests.swift
@@ -1,9 +1,8 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("CGATS Parser & Writer")
-struct CGATSParserTests {
+final class CGATSParserTests: XCTestCase {
 
     private static let canonicalCTI3 = """
     CTI3
@@ -21,44 +20,40 @@ struct CGATSParserTests {
     END_DATA
     """
 
-    @Test("Parses CTI3 with canonical field names")
-    func parseCTI3() throws {
+    func testParseCTI3() throws {
         let dataset = try CGATSParser.parse(Self.canonicalCTI3)
-        #expect(dataset.format == .cti3)
-        #expect(dataset.samples.count == 2)
-        #expect(dataset.colorRep == "RGB")
-        #expect(dataset.deviceClass == "DISPLAY")
-        #expect(dataset.samples[0].id == "1")
-        #expect(dataset.samples[0].loc == "A1")
-        #expect(dataset.samples[1].values["RGB_G"] == "50.0000")
+        XCTAssertEqual(dataset.format, .cti3)
+        XCTAssertEqual(dataset.samples.count, 2)
+        XCTAssertEqual(dataset.colorRep, "RGB")
+        XCTAssertEqual(dataset.deviceClass, "DISPLAY")
+        XCTAssertEqual(dataset.samples[0].id, "1")
+        XCTAssertEqual(dataset.samples[0].loc, "A1")
+        XCTAssertEqual(dataset.samples[1].values["RGB_G"], "50.0000")
     }
 
-    @Test("Round-trips parse, write, reparse")
-    func roundTrip() throws {
+    func testRoundTrip() throws {
         let first = try CGATSParser.parse(Self.canonicalCTI3)
         let text = try CGATSWriter.write(first)
         let second = try CGATSParser.parse(text)
-        #expect(second.format == first.format)
-        #expect(second.samples.count == first.samples.count)
-        #expect(second.colorRep == first.colorRep)
-        #expect(second.deviceClass == first.deviceClass)
+        XCTAssertEqual(second.format, first.format)
+        XCTAssertEqual(second.samples.count, first.samples.count)
+        XCTAssertEqual(second.colorRep, first.colorRep)
+        XCTAssertEqual(second.deviceClass, first.deviceClass)
     }
 
-    @Test("Parses CSV with comma delimiters")
-    func parseCSV() throws {
+    func testParseCSV() throws {
         let csv = """
         SAMPLE_ID,SAMPLE_LOC,RGB_R,RGB_G,RGB_B,XYZ_X,XYZ_Y,XYZ_Z,LAB_L,LAB_A,LAB_B
         1,A1,50,0,0,20,10,5,50,60,30
         2,A2,0,50,0,10,30,5,60,-50,40
         """
         let dataset = try CGATSParser.parse(csv, sourceURL: URL(fileURLWithPath: "/tmp/sample.csv"))
-        #expect(dataset.format == .csv)
-        #expect(dataset.samples.count == 2)
-        #expect(dataset.samples[0].values["RGB_R"] == "50.0000")
+        XCTAssertEqual(dataset.format, .csv)
+        XCTAssertEqual(dataset.samples.count, 2)
+        XCTAssertEqual(dataset.samples[0].values["RGB_R"], "50.0000")
     }
 
-    @Test("Converts 0-255 device values to 0-100")
-    func converts255To100() throws {
+    func testConverts255To100() throws {
         let rgb = """
         CTI3
         COLOR_REP RGB
@@ -72,12 +67,11 @@ struct CGATSParserTests {
         END_DATA
         """
         let dataset = try CGATSParser.parse(rgb)
-        #expect(dataset.samples[0].values["RGB_R"] == "100.0000")
-        #expect(dataset.samples[0].values["RGB_G"] == "50.1961")
+        XCTAssertEqual(dataset.samples[0].values["RGB_R"], "100.0000")
+        XCTAssertEqual(dataset.samples[0].values["RGB_G"], "50.1961")
     }
 
-    @Test("Synthesizes COLOR_REP and DEVICE_CLASS when missing")
-    func synthesizesMetadata() throws {
+    func testSynthesizesMetadata() throws {
         let cmyk = """
         CTI3
         NUMBER_OF_FIELDS 6
@@ -90,19 +84,15 @@ struct CGATSParserTests {
         END_DATA
         """
         let dataset = try CGATSParser.parse(cmyk)
-        #expect(dataset.colorRep == "CMYK")
-        #expect(dataset.deviceClass == "PRINTER")
+        XCTAssertEqual(dataset.colorRep, "CMYK")
+        XCTAssertEqual(dataset.deviceClass, "PRINTER")
     }
 
-    @Test("Rejects empty file")
-    func rejectsEmpty() {
-        #expect(throws: (any Error).self) {
-            _ = try CGATSParser.parse("")
-        }
+    func testRejectsEmpty() {
+        XCTAssertThrowsError(try CGATSParser.parse(""))
     }
 
-    @Test("Rejects malformed arity")
-    func rejectsArity() {
+    func testRejectsArity() {
         let bad = """
         CTI3
         NUMBER_OF_FIELDS 2
@@ -114,21 +104,18 @@ struct CGATSParserTests {
         1
         END_DATA
         """
-        #expect(throws: (any Error).self) {
-            _ = try CGATSParser.parse(bad)
-        }
+        XCTAssertThrowsError(try CGATSParser.parse(bad))
     }
 
-    @Test("Writer emits valid .ti3 with tabs and required keywords")
-    func writerFormat() throws {
+    func testWriterFormat() throws {
         let dataset = try CGATSParser.parse(Self.canonicalCTI3)
         let text = try CGATSWriter.write(dataset)
-        #expect(text.contains("CTI3"))
-        #expect(text.contains("BEGIN_DATA_FORMAT"))
-        #expect(text.contains("BEGIN_DATA"))
-        #expect(text.contains("END_DATA"))
-        #expect(text.contains("COLOR_REP"))
-        #expect(text.contains("DEVICE_CLASS"))
-        #expect(text.contains("\t"))
+        XCTAssertTrue(text.contains("CTI3"))
+        XCTAssertTrue(text.contains("BEGIN_DATA_FORMAT"))
+        XCTAssertTrue(text.contains("BEGIN_DATA"))
+        XCTAssertTrue(text.contains("END_DATA"))
+        XCTAssertTrue(text.contains("COLOR_REP"))
+        XCTAssertTrue(text.contains("DEVICE_CLASS"))
+        XCTAssertTrue(text.contains("\t"))
     }
 }
diff --git a/Tests/ICCeryCoreTests/CalibrationIdentityTests.swift b/Tests/ICCeryCoreTests/CalibrationIdentityTests.swift
index 4422e87..2f2da4b 100644
--- a/Tests/ICCeryCoreTests/CalibrationIdentityTests.swift
+++ b/Tests/ICCeryCoreTests/CalibrationIdentityTests.swift
@@ -1,78 +1,67 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
 /// Issue #83 — canonical `CAL_` / original-stem pairing.
-@Suite("CalibrationIdentity")
-struct CalibrationIdentityTests {
-    @Test("live foo, no persisted")
-    func livePlain() {
+final class CalibrationIdentityTests: XCTestCase {
+    func testLivePlain() {
         let id = CalibrationIdentity.parse(liveBasename: "foo", persistedOriginal: "")
-        #expect(id.originalBasename == "foo")
-        #expect(id.calibrationBasename == "CAL_foo")
+        XCTAssertEqual(id.originalBasename, "foo")
+        XCTAssertEqual(id.calibrationBasename, "CAL_foo")
     }
 
-    @Test("live foo ignores stale persisted")
-    func livePlainIgnoresPersisted() {
+    func testLivePlainIgnoresPersisted() {
         let id = CalibrationIdentity.parse(liveBasename: "foo", persistedOriginal: "bar")
-        #expect(id.originalBasename == "foo")
-        #expect(id.calibrationBasename == "CAL_foo")
+        XCTAssertEqual(id.originalBasename, "foo")
+        XCTAssertEqual(id.calibrationBasename, "CAL_foo")
     }
 
-    @Test("live CAL_foo, persisted foo")
-    func liveCalPersisted() {
+    func testLiveCalPersisted() {
         let id = CalibrationIdentity.parse(liveBasename: "CAL_foo", persistedOriginal: "foo")
-        #expect(id.originalBasename == "foo")
-        #expect(id.calibrationBasename == "CAL_foo")
+        XCTAssertEqual(id.originalBasename, "foo")
+        XCTAssertEqual(id.calibrationBasename, "CAL_foo")
     }
 
-    @Test("live CAL_foo, empty persisted strips prefix")
-    func liveCalNoPersist() {
+    func testLiveCalNoPersist() {
         let id = CalibrationIdentity.parse(liveBasename: "CAL_foo", persistedOriginal: "")
-        #expect(id.originalBasename == "foo")
-        #expect(id.calibrationBasename == "CAL_foo")
+        XCTAssertEqual(id.originalBasename, "foo")
+        XCTAssertEqual(id.calibrationBasename, "CAL_foo")
     }
 
-    @Test("persisted original wins over CAL_ live")
-    func persistedWins() {
+    func testPersistedWins() {
         let id = CalibrationIdentity.parse(liveBasename: "CAL_foo", persistedOriginal: "bar")
-        #expect(id.originalBasename == "bar")
-        #expect(id.calibrationBasename == "CAL_bar")
+        XCTAssertEqual(id.originalBasename, "bar")
+        XCTAssertEqual(id.calibrationBasename, "CAL_bar")
     }
 
-    @Test("empty live yields empty identity even with persisted original")
-    func emptyLiveWithPersisted() {
+    func testEmptyLiveWithPersisted() {
         let id = CalibrationIdentity.parse(liveBasename: "", persistedOriginal: "foo")
-        #expect(id.originalBasename.isEmpty)
-        #expect(id.calibrationBasename.isEmpty)
+        XCTAssertTrue(id.originalBasename.isEmpty)
+        XCTAssertTrue(id.calibrationBasename.isEmpty)
     }
 
-    @Test("empty live, empty persisted")
-    func emptyLive() {
+    func testEmptyLive() {
         let id = CalibrationIdentity.parse(liveBasename: "", persistedOriginal: "")
-        #expect(id.originalBasename.isEmpty)
-        #expect(id.calibrationBasename.isEmpty)
+        XCTAssertTrue(id.originalBasename.isEmpty)
+        XCTAssertTrue(id.calibrationBasename.isEmpty)
     }
 
-    @Test("prefix is idempotent on already-prefixed input")
-    func alreadyPrefixed() {
-        #expect(CalibrationIdentity.prefix("CAL_foo") == "CAL_foo")
-        #expect(CalibrationIdentity.prefix("foo") == "CAL_foo")
+    func testAlreadyPrefixed() {
+        XCTAssertEqual(CalibrationIdentity.prefix("CAL_foo"), "CAL_foo")
+        XCTAssertEqual(CalibrationIdentity.prefix("foo"), "CAL_foo")
         let id = CalibrationIdentity.parse(liveBasename: "CAL_CAL_foo", persistedOriginal: "")
-        #expect(id.originalBasename == "CAL_foo")
-        #expect(id.calibrationBasename == "CAL_foo")
+        XCTAssertEqual(id.originalBasename, "CAL_foo")
+        XCTAssertEqual(id.calibrationBasename, "CAL_foo")
     }
 
-    @Test("prefix never invents a name from empty input")
-    func prefixEmpty() {
-        #expect(CalibrationIdentity.prefix("").isEmpty)
-        #expect(CalibrationIdentity.strip("foo") == "foo")
-        #expect(CalibrationIdentity.strip("CAL_foo") == "foo")
+    func testPrefixEmpty() {
+        XCTAssertTrue(CalibrationIdentity.prefix("").isEmpty)
+        XCTAssertEqual(CalibrationIdentity.strip("foo"), "foo")
+        XCTAssertEqual(CalibrationIdentity.strip("CAL_foo"), "foo")
     }
 
-    @Test("runner process id for a calibration targen is targen_CAL_*")
-    func processIdMatches() {
+    func testProcessIdMatches() {
         let cal = CalibrationIdentity.prefix("foo")
-        #expect(ProcessID.targen(cal) == "targen_CAL_foo")
+        XCTAssertEqual(ProcessID.targen(cal), "targen_CAL_foo")
     }
 }
diff --git a/Tests/ICCeryCoreTests/CalibrationTargenArgsTests.swift b/Tests/ICCeryCoreTests/CalibrationTargenArgsTests.swift
index c43313a..1739444 100644
--- a/Tests/ICCeryCoreTests/CalibrationTargenArgsTests.swift
+++ b/Tests/ICCeryCoreTests/CalibrationTargenArgsTests.swift
@@ -1,12 +1,10 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("CalibrationTargenArgs")
-struct CalibrationTargenArgsTests {
+final class CalibrationTargenArgsTests: XCTestCase {
 
-    @Test("RGB baseline")
-    func rgbBaseline() throws {
+    func testRgbBaseline() throws {
         let config = CalibrationTargenConfig(
             colourSpace: .rgb,
             steps: 21,
@@ -15,11 +13,10 @@ struct CalibrationTargenArgsTests {
             workingDirectory: URL(fileURLWithPath: "/tmp")
         )
         let args = try CalibrationTargenArgs.build(config: config)
-        #expect(args == ["-v", "-d", "2", "-s", "21", "-g", "21", "-e", "4", "-f", "0", "CAL_demo"])
+        XCTAssertEqual(args, ["-v", "-d", "2", "-s", "21", "-g", "21", "-e", "4", "-f", "0", "CAL_demo"])
     }
 
-    @Test("CMYK baseline with ink limit and neutral emphasis")
-    func cmykWithOptions() throws {
+    func testCmykWithOptions() throws {
         let config = CalibrationTargenConfig(
             colourSpace: .cmyk,
             steps: 25,
@@ -30,33 +27,26 @@ struct CalibrationTargenArgsTests {
             workingDirectory: URL(fileURLWithPath: "/tmp")
         )
         let args = try CalibrationTargenArgs.build(config: config)
-        #expect(args == ["-v", "-d", "4", "-s", "25", "-g", "25", "-e", "4", "-f", "0", "-n", "25", "-l", "320", "CAL_printer"])
+        XCTAssertEqual(args, ["-v", "-d", "4", "-s", "25", "-g", "25", "-e", "4", "-f", "0", "-n", "25", "-l", "320", "CAL_printer"])
     }
 
-    @Test("Rejects out-of-range steps")
-    func rejectsBadSteps() {
+    func testRejectsBadSteps() {
         let config = CalibrationTargenConfig(steps: 5, basename: "demo")
-        #expect(throws: (any Error).self) {
-            _ = try CalibrationTargenArgs.build(config: config)
-        }
+        XCTAssertThrowsError(try CalibrationTargenArgs.build(config: config))
     }
 
-    @Test("Rejects bad CMYK ink limit")
-    func rejectsBadInkLimit() {
+    func testRejectsBadInkLimit() {
         let config = CalibrationTargenConfig(
             colourSpace: .cmyk,
             inkLimit: 500,
             basename: "demo"
         )
-        #expect(throws: (any Error).self) {
-            _ = try CalibrationTargenArgs.build(config: config)
-        }
+        XCTAssertThrowsError(try CalibrationTargenArgs.build(config: config))
     }
 
-    @Test("Does not double-prefix an existing CAL_ basename")
-    func noDoublePrefix() throws {
+    func testNoDoublePrefix() throws {
         let config = CalibrationTargenConfig(basename: "CAL_test")
         let args = try CalibrationTargenArgs.build(config: config)
-        #expect(args.last == "CAL_test")
+        XCTAssertEqual(args.last, "CAL_test")
     }
 }
diff --git a/Tests/ICCeryCoreTests/ColprofArgsTests.swift b/Tests/ICCeryCoreTests/ColprofArgsTests.swift
index 9b4f0f7..653e674 100644
--- a/Tests/ICCeryCoreTests/ColprofArgsTests.swift
+++ b/Tests/ICCeryCoreTests/ColprofArgsTests.swift
@@ -1,72 +1,63 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("ColprofArgs")
-struct ColprofArgsTests {
+final class ColprofArgsTests: XCTestCase {
 
-    @Test("Default algorithm and quality")
-    func defaults() throws {
+    func testDefaults() throws {
         let config = ColprofConfig(basename: "target")
         let args = try ColprofArgs.build(config: config)
-        #expect(args == ["-v", "-a", "l", "-q", "m", "target"])
+        XCTAssertEqual(args, ["-v", "-a", "l", "-q", "m", "target"])
     }
 
-    @Test("FWA bare -f when empty string")
-    func fwaBareFlag() throws {
+    func testFwaBareFlag() throws {
         let config = ColprofConfig(fwa: "", basename: "target")
         let args = try ColprofArgs.build(config: config)
-        #expect(args == ["-v", "-a", "l", "-q", "m", "-f", "target"])
+        XCTAssertEqual(args, ["-v", "-a", "l", "-q", "m", "-f", "target"])
     }
 
-    @Test("FWA D50 and D65 emit -f value")
-    func fwaD50() throws {
+    func testFwaD50() throws {
         let config = ColprofConfig(fwa: "D50", basename: "target")
         let args = try ColprofArgs.build(config: config)
-        #expect(args.contains("-f"))
-        #expect(args.contains("D50"))
-        #expect(args.last == "target")
+        XCTAssertTrue(args.contains("-f"))
+        XCTAssertTrue(args.contains("D50"))
+        XCTAssertEqual(args.last, "target")
     }
 
-    @Test("FWA none is omitted")
-    func fwaNoneOmitted() throws {
+    func testFwaNoneOmitted() throws {
         let config = ColprofConfig(fwa: "none", basename: "target")
         let args = try ColprofArgs.build(config: config)
-        #expect(!args.contains("-f"))
+        XCTAssertFalse(args.contains("-f"))
     }
 
-    @Test("Viewing conditions skip none")
-    func viewingCondNoneSkipped() throws {
+    func testViewingCondNoneSkipped() throws {
         let config = ColprofConfig(
             inputViewingCond: "none",
             outputViewingCond: "mt",
             basename: "target"
         )
         let args = try ColprofArgs.build(config: config)
-        #expect(!args.contains("-c"))
-        #expect(args.contains("-d"))
-        #expect(args.contains("mt"))
+        XCTAssertFalse(args.contains("-c"))
+        XCTAssertTrue(args.contains("-d"))
+        XCTAssertTrue(args.contains("mt"))
     }
 
-    @Test("Description falls back to basename when empty")
-    func descriptionFallback() throws {
+    func testDescriptionFallback() throws {
         let config = ColprofConfig(description: "", basename: "target")
         let args = try ColprofArgs.build(config: config)
-        #expect(!args.contains("-D"))
+        XCTAssertFalse(args.contains("-D"))
     }
 
-    @Test("Copyright only when non-empty")
-    func copyright() throws {
+    func testCopyright() throws {
         let config = ColprofConfig(copyright: "Gronod 2026", basename: "target")
         let args = try ColprofArgs.build(config: config)
-        #expect(args.contains("-C"))
-        #expect(args.contains("Gronod 2026"))
+        XCTAssertTrue(args.contains("-C"))
+        XCTAssertTrue(args.contains("Gronod 2026"))
     }
 
-    @Test("No -u passed")
-    func noProgressJsonFlag() throws {
+    func testNoProgressJsonFlag() throws {
         let config = ColprofConfig(basename: "target")
         let args = try ColprofArgs.build(config: config)
-        #expect(!args.contains("-u"))
+        XCTAssertFalse(args.contains("-u"))
     }
 }
diff --git a/Tests/ICCeryCoreTests/ColprofProgressTests.swift b/Tests/ICCeryCoreTests/ColprofProgressTests.swift
index 922cf53..66f7b31 100644
--- a/Tests/ICCeryCoreTests/ColprofProgressTests.swift
+++ b/Tests/ICCeryCoreTests/ColprofProgressTests.swift
@@ -1,24 +1,20 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("ColprofProgress")
-struct ColprofProgressTests {
+final class ColprofProgressTests: XCTestCase {
 
-    @Test("Classifies gamut mapping")
-    func gamutMapping() {
-        #expect(ColprofProgressClassifier.classify(line: "Gamut mapping calculation in progress") == .gamutMapping)
+    func testGamutMapping() {
+        XCTAssertEqual(ColprofProgressClassifier.classify(line: "Gamut mapping calculation in progress"), .gamutMapping)
     }
 
-    @Test("Classifies fitting or clut")
-    func fitting() {
-        #expect(ColprofProgressClassifier.classify(line: "Fitting cLUT grid points") == .fittingClut)
-        #expect(ColprofProgressClassifier.classify(line: "clut table") == .fittingClut)
+    func testFitting() {
+        XCTAssertEqual(ColprofProgressClassifier.classify(line: "Fitting cLUT grid points"), .fittingClut)
+        XCTAssertEqual(ColprofProgressClassifier.classify(line: "clut table"), .fittingClut)
     }
 
-    @Test("Classifies writing")
-    func writing() {
-        #expect(ColprofProgressClassifier.classify(line: "Writing ICC profile header") == .writingIcc)
-        #expect(ColprofProgressClassifier.classify(line: "icc profile written") == .writingIcc)
+    func testWriting() {
+        XCTAssertEqual(ColprofProgressClassifier.classify(line: "Writing ICC profile header"), .writingIcc)
+        XCTAssertEqual(ColprofProgressClassifier.classify(line: "icc profile written"), .writingIcc)
     }
 }
diff --git a/Tests/ICCeryCoreTests/CupsOptionsFilterTests.swift b/Tests/ICCeryCoreTests/CupsOptionsFilterTests.swift
index 52498d3..0f035da 100644
--- a/Tests/ICCeryCoreTests/CupsOptionsFilterTests.swift
+++ b/Tests/ICCeryCoreTests/CupsOptionsFilterTests.swift
@@ -1,4 +1,4 @@
-import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 @testable import ICCery
@@ -6,48 +6,42 @@ import AppKit
 import ApplicationServices
 
 /// Issue 14 — PMPrintSettingsToOptions capture filter (docs/11 layer ⑥).
-@Suite("CupsOptionsFilter")
-struct CupsOptionsFilterTests {
+final class CupsOptionsFilterTests: XCTestCase {
 
-    @Test("Drops com.apple.*, collate, copies, job-sheets, AP_* keys")
-    func dropsReserved() {
+    func testDropsReserved() {
         let raw = "AP_ColorMatchingMode=AP_ApplicationColorMatching "
             + "AP.ColorMatchingMode=AP_ApplicationColorMatching "
             + "com.apple.print.JobTicket.PMTotalSidesImaged=0 "
             + "collate=true copies=1 job-sheets=none,none "
             + "pserrorhandler-requested=standard "
             + "MediaType=PhotographicGlossy"
-        #expect(CupsOptionsFilter.filter(raw) == "MediaType=PhotographicGlossy")
+        XCTAssertEqual(CupsOptionsFilter.filter(raw), "MediaType=PhotographicGlossy")
     }
 
-    @Test("Keeps relevant driver keys, order preserved")
-    func keepsRelevant() {
+    func testKeepsRelevant() {
         let raw = "InputSlot=Rear PageSize=A4 CNIJIntent2=4 "
             + "Resolution=600x600dpi Duplex=None"
-        #expect(CupsOptionsFilter.filter(raw) == raw)
+        XCTAssertEqual(CupsOptionsFilter.filter(raw), raw)
     }
 
-    @Test("Permissive: unknown non-com.* keys survive")
-    func keepsUnknown() {
+    func testKeepsUnknown() {
         let raw = "VendorFooBar=baz MediaType=Plain"
-        #expect(CupsOptionsFilter.filter(raw) == raw)
+        XCTAssertEqual(CupsOptionsFilter.filter(raw), raw)
     }
 
-    @Test("Drops empty keys and values")
-    func dropsEmpty() {
+    func testDropsEmpty() {
         let raw = "=noval MediaType= InputSlot=Rear"
         // "MediaType=" has an empty value → dropped; "=noval" empty key.
-        #expect(CupsOptionsFilter.filter(raw) == "InputSlot=Rear")
+        XCTAssertEqual(CupsOptionsFilter.filter(raw), "InputSlot=Rear")
     }
 
-    @Test("extractMediaType prefers MediaType then EPIJ_Medi")
-    func extractMedia() {
-        #expect(CupsParsers.extractMediaType(
-            fromOptionsString: "MediaType=Photo EPIJ_Medi=1") == "Photo")
-        #expect(CupsParsers.extractMediaType(
-            fromOptionsString: "EPIJ_Medi=7") == "7")
-        #expect(CupsParsers.extractMediaType(
-            fromOptionsString: "PageSize=A4") == nil)
+    func testExtractMedia() {
+        XCTAssertEqual(CupsParsers.extractMediaType(
+            fromOptionsString: "MediaType=Photo EPIJ_Medi=1"), "Photo")
+        XCTAssertEqual(CupsParsers.extractMediaType(
+            fromOptionsString: "EPIJ_Medi=7"), "7")
+        XCTAssertNil(CupsParsers.extractMediaType(
+            fromOptionsString: "PageSize=A4"))
     }
 }
 
@@ -55,9 +49,8 @@ struct CupsOptionsFilterTests {
 /// `@convention(c)` closures can't capture, so recording goes through
 /// a file-scope recorder keyed by global state; no private symbols are
 /// touched.
-@Suite("ColorSyncSuppressor")
 @MainActor
-struct ColorSyncSuppressorTests {
+final class ColorSyncSuppressorTests: XCTestCase {
 
     /// Fake PMPrintSession — the injected resolver never dereferences it.
     private var fakeSession: PMPrintSession {
@@ -90,55 +83,50 @@ struct ColorSyncSuppressorTests {
         return s
     }
 
-    @Test("Attempt order: Lock → Mode → NoLock, AP_ prefix first")
-    func attemptOrder() {
+    func testAttemptOrder() {
         Self.recorded = []
         Self.succeeding = nil
         Self.missing = ["PMSessionSetColorMatchingModeLock"]
         let s = makeSuppressor()
-        #expect(s.applySPIMode(to: fakeSession) == false)
+        XCTAssertEqual(s.applySPIMode(to: fakeSession), false)
         // Lock is unresolvable → skipped; the rest plays out in order.
-        #expect(Self.recorded.map { "\($0.0)|\($0.1)" }
-            == ColorMatchingAttempts.attempts
+        XCTAssertEqual(Self.recorded.map { "\($0.0)|\($0.1)" }, ColorMatchingAttempts.attempts
                 .filter { $0.symbol != "PMSessionSetColorMatchingModeLock" }
                 .map { "\($0.symbol)|\($0.mode)" })
     }
 
-    @Test("First zero wins — later symbols/modes not called")
-    func firstZeroWins() {
+    func testFirstZeroWins() {
         Self.recorded = []
         Self.succeeding = ("PMSessionSetColorMatchingModeLock",
                            "AP_ApplicationColorMatching")
         Self.missing = []
         let s = makeSuppressor()
-        #expect(s.applySPIMode(to: fakeSession))
-        #expect(Self.recorded.map { "\($0.0)|\($0.1)" } == [
+        XCTAssertTrue(s.applySPIMode(to: fakeSession))
+        XCTAssertEqual(Self.recorded.map { "\($0.0)|\($0.1)" }, [
             "PMSessionSetColorMatchingModeLock|AP_ApplicationColorMatching",
         ])
     }
 
-    @Test("Mode fallback: AP_ rejected → ApplicationColorMatching tried")
-    func modeFallback() {
+    func testModeFallback() {
         Self.recorded = []
         Self.succeeding = ("PMSessionSetColorMatchingModeLock",
                            "ApplicationColorMatching")
         Self.missing = []
         let s = makeSuppressor()
-        #expect(s.applySPIMode(to: fakeSession))
-        #expect(Self.recorded[0].0 == "PMSessionSetColorMatchingModeLock")
-        #expect(Self.recorded[0].1 == "AP_ApplicationColorMatching")
-        #expect(Self.recorded[1].0 == "PMSessionSetColorMatchingModeLock")
-        #expect(Self.recorded[1].1 == "ApplicationColorMatching")
-        #expect(Self.recorded.count == 2)
+        XCTAssertTrue(s.applySPIMode(to: fakeSession))
+        XCTAssertEqual(Self.recorded[0].0, "PMSessionSetColorMatchingModeLock")
+        XCTAssertEqual(Self.recorded[0].1, "AP_ApplicationColorMatching")
+        XCTAssertEqual(Self.recorded[1].0, "PMSessionSetColorMatchingModeLock")
+        XCTAssertEqual(Self.recorded[1].1, "ApplicationColorMatching")
+        XCTAssertEqual(Self.recorded.count, 2)
     }
 
-    @Test("All symbols missing → false, no calls")
-    func allMissing() {
+    func testAllMissing() {
         Self.recorded = []
         Self.succeeding = nil
         Self.missing = Set(ColorMatchingAttempts.symbols)
         let s = makeSuppressor()
-        #expect(s.applySPIMode(to: fakeSession) == false)
-        #expect(Self.recorded.isEmpty)
+        XCTAssertEqual(s.applySPIMode(to: fakeSession), false)
+        XCTAssertTrue(Self.recorded.isEmpty)
     }
 }
diff --git a/Tests/ICCeryCoreTests/CupsParserTests.swift b/Tests/ICCeryCoreTests/CupsParserTests.swift
index fdf948f..a4be264 100644
--- a/Tests/ICCeryCoreTests/CupsParserTests.swift
+++ b/Tests/ICCeryCoreTests/CupsParserTests.swift
@@ -1,11 +1,10 @@
-import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 
 /// Issue 12 — CUPS enumeration parsers on recorded fixtures
 /// (docs/10–11). No live `lpstat`/`lpoptions` is spawned here.
-@Suite("CupsParsers")
-struct CupsParsersTests {
+final class CupsParsersTests: XCTestCase {
 
     // Recorded on an Epson XP-55 + Canon Pro9500 host.
     private let lpstatE = """
@@ -34,112 +33,102 @@ struct CupsParsersTests {
         cupsPrintQuality/cupsPrintQuality: Draft *Normal High
         """
 
-    @Test("lpstat -e: one destination per line; empty = success")
-    func destinations() {
-        #expect(CupsParsers.lpstatDestinations(lpstatE) == [
+    func testDestinations() {
+        XCTAssertEqual(CupsParsers.lpstatDestinations(lpstatE), [
             "Canon_Pro9500_II_series_XPS",
             "Epson_XP_55_LPD",
             "EPSON_XP_55_Series",
         ])
-        #expect(CupsParsers.lpstatDestinations("") == [])
+        XCTAssertEqual(CupsParsers.lpstatDestinations(""), [])
     }
 
-    @Test("lpstat -p: idle / now-printing / disabled statuses")
-    func statuses() {
+    func testStatuses() {
         let s = CupsParsers.lpstatStatuses(lpstatP)
-        #expect(s["Canon_Pro9500_II_series_XPS"] == .idle)
-        #expect(s["Epson_XP_55_LPD"] == .printing)
-        #expect(s["EPSON_XP_55_Series"] == .stopped)
+        XCTAssertEqual(s["Canon_Pro9500_II_series_XPS"], .idle)
+        XCTAssertEqual(s["Epson_XP_55_LPD"], .printing)
+        XCTAssertEqual(s["EPSON_XP_55_Series"], .stopped)
     }
 
-    @Test("lpstat -d: default destination or none")
-    func defaultDestination() {
-        #expect(CupsParsers.lpstatDefault(
-            "system default destination: Canon_Pro9500_II_series_XPS\n")
-            == "Canon_Pro9500_II_series_XPS")
-        #expect(CupsParsers.lpstatDefault("no system default destination\n") == nil)
+    func testDefaultDestination() {
+        XCTAssertEqual(CupsParsers.lpstatDefault(
+            "system default destination: Canon_Pro9500_II_series_XPS\n"), "Canon_Pro9500_II_series_XPS")
+        XCTAssertNil(CupsParsers.lpstatDefault("no system default destination\n"))
     }
 
-    @Test("lpoptions -p: quoted printer-info, bare flags ignored")
-    func displayName() {
-        #expect(CupsParsers.lpoptionsDisplayName(lpoptionsP) == "EPSON XP-55 Series")
-        #expect(CupsParsers.lpoptionsDisplayName("printer-type=42\n") == nil)
+    func testDisplayName() {
+        XCTAssertEqual(CupsParsers.lpoptionsDisplayName(lpoptionsP), "EPSON XP-55 Series")
+        XCTAssertNil(CupsParsers.lpoptionsDisplayName("printer-type=42\n"))
     }
 
-    @Test("lpoptions -l: key/label split, * marks the default")
-    func optionListings() {
+    func testOptionListings() {
         let listings = CupsParsers.lpoptionsList(lpoptionsL)
-        #expect(listings.count == 6)
+        XCTAssertEqual(listings.count, 6)
 
         let page = listings[0]
-        #expect(page.key == "PageSize")
-        #expect(page.label == "Media Size")
-        #expect(page.defaultChoice == "A4")
-        #expect(page.choices.contains("Custom.WIDTHxHEIGHT"))
-        #expect(!page.choices.contains("*A4"))
+        XCTAssertEqual(page.key, "PageSize")
+        XCTAssertEqual(page.label, "Media Size")
+        XCTAssertEqual(page.defaultChoice, "A4")
+        XCTAssertTrue(page.choices.contains("Custom.WIDTHxHEIGHT"))
+        XCTAssertFalse(page.choices.contains("*A4"))
 
         let slot = listings[1]
-        #expect(slot.key == "InputSlot")
-        #expect(slot.choices == ["Auto", "Main", "Photo", "Rear"])
-        #expect(slot.defaultChoice == "Main")
+        XCTAssertEqual(slot.key, "InputSlot")
+        XCTAssertEqual(slot.choices, ["Auto", "Main", "Photo", "Rear"])
+        XCTAssertEqual(slot.defaultChoice, "Main")
     }
 
-    @Test("capabilities: trays/sizes index 1-based, media uses detected key")
-    func capabilities() {
+    func testCapabilities() {
         let service = CupsService()
         let listings = CupsParsers.lpoptionsList(lpoptionsL)
         let caps = service.capabilities(from: listings, ppd: nil)
 
-        #expect(caps.trays == [
+        XCTAssertEqual(caps.trays, [
             PrinterTray(id: 1, name: "Auto"),
             PrinterTray(id: 2, name: "Main"),
             PrinterTray(id: 3, name: "Photo"),
             PrinterTray(id: 4, name: "Rear"),
         ])
-        #expect(caps.paperSizes.first == PrinterPaperSize(id: 1, name: "3.5x5"))
-        #expect(caps.paperSizes.count == 10)
-        #expect(caps.mediaTypes.map(\.id) == [
+        XCTAssertEqual(caps.paperSizes.first, PrinterPaperSize(id: 1, name: "3.5x5"))
+        XCTAssertEqual(caps.paperSizes.count, 10)
+        XCTAssertEqual(caps.mediaTypes.map(\.id), [
             "Stationery", "PhotographicHighGloss", "Photographic",
             "PhotographicMatte", "Envelope",
         ])
-        #expect(caps.supportsOrientation)
+        XCTAssertTrue(caps.supportsOrientation)
     }
 
-    @Test("PPD enrichment maps id → human label")
-    func ppdLabels() {
+    func testPpdLabels() {
         let ppd = """
             *CNIJMediaType 42/Photo Paper Plus Semi-gloss: "<</MediaType(42)>>"
             *CNIJMediaType 0/Plain Paper: ""
             *en_US.CNIJMediaType 13/Envelope: ""
             """
         let labels = CupsParsers.ppdChoiceLabels(ppd, key: "CNIJMediaType")
-        #expect(labels["42"] == "Photo Paper Plus Semi-gloss")
-        #expect(labels["0"] == "Plain Paper")
-        #expect(labels["13"] == "Envelope")
+        XCTAssertEqual(labels["42"], "Photo Paper Plus Semi-gloss")
+        XCTAssertEqual(labels["0"], "Plain Paper")
+        XCTAssertEqual(labels["13"], "Envelope")
     }
 
-    @Test("detectMediaTypeKey prefers vendor keys in order")
-    func mediaTypeKey() {
-        #expect(CupsParsers.detectMediaTypeKey(
-            optionKeys: ["MediaType", "CNIJMediaType"]) == "CNIJMediaType")
-        #expect(CupsParsers.detectMediaTypeKey(
-            optionKeys: ["PageSize", "MediaType"]) == "MediaType")
-        #expect(CupsParsers.detectMediaTypeKey(optionKeys: ["PageSize"]) == nil)
+    func testMediaTypeKey() {
+        XCTAssertEqual(CupsParsers.detectMediaTypeKey(
+            optionKeys: ["MediaType", "CNIJMediaType"]), "CNIJMediaType")
+        XCTAssertEqual(CupsParsers.detectMediaTypeKey(
+            optionKeys: ["PageSize", "MediaType"]), "MediaType")
+        XCTAssertNil(CupsParsers.detectMediaTypeKey(optionKeys: ["PageSize"]))
     }
 
-    @Test("Driver bypass: Canon Intent2 > Intent; Epson CCor > CMat")
-    func driverBypass() {
+    func testDriverBypass() {
         func pair(_ keys: Set<String>) -> String? {
             CupsParsers.detectDriverColorBypass(optionKeys: keys)
                 .map { "\($0.key)=\($0.value)" }
         }
-        #expect(pair(["CNIJIntent2", "CNIJIntent"]) == "CNIJIntent2=4")
-        #expect(pair(["CNIJIntent"]) == "CNIJIntent=4")
-        #expect(pair(["EPIJ_CCor", "EPIJ_CMat"]) == "EPIJ_CCor=0")
-        #expect(pair(["EPIJ_CMat"]) == "EPIJ_CMat=3")
-        #expect(pair(["StpColorCorrection"]) == "StpColorCorrection=Uncorrected")
-        #expect(pair(["ColorCorrection"]) == "ColorCorrection=Uncorrected")
-        #expect(pair(["EpsonColorMode"]) == "EpsonColorMode=Off")
-        #expect(pair(["PageSize"]) == nil)
+        XCTAssertEqual(pair(["CNIJIntent2", "CNIJIntent"]), "CNIJIntent2=4")
+        XCTAssertEqual(pair(["CNIJIntent"]), "CNIJIntent=4")
+        XCTAssertEqual(pair(["EPIJ_CCor", "EPIJ_CMat"]), "EPIJ_CCor=0")
+        XCTAssertEqual(pair(["EPIJ_CMat"]), "EPIJ_CMat=3")
+        XCTAssertEqual(pair(["StpColorCorrection"]), "StpColorCorrection=Uncorrected")
+        XCTAssertEqual(pair(["ColorCorrection"]), "ColorCorrection=Uncorrected")
+        XCTAssertEqual(pair(["EpsonColorMode"]), "EpsonColorMode=Off")
+        XCTAssertNil(pair(["PageSize"]))
     }
 }
diff --git a/Tests/ICCeryCoreTests/DriftAlertTests.swift b/Tests/ICCeryCoreTests/DriftAlertTests.swift
index 4eb2835..11fb145 100644
--- a/Tests/ICCeryCoreTests/DriftAlertTests.swift
+++ b/Tests/ICCeryCoreTests/DriftAlertTests.swift
@@ -1,65 +1,57 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("DriftAlert")
-struct DriftAlertTests {
+final class DriftAlertTests: XCTestCase {
 
-    @Test("No alert with fewer than two poor results")
-    func notEnough() {
+    func testNotEnough() {
         let records = [
             record(avg: 4.0, at: 1000)
         ]
-        #expect(DriftAlert.compute(from: records) == nil)
+        XCTAssertNil(DriftAlert.compute(from: records))
     }
 
-    @Test("Alert on two poor results one hour apart")
-    func oneHourApart() {
+    func testOneHourApart() {
         let records = [
             record(avg: 4.0, at: 1000),
             record(avg: 5.0, at: 4600)
         ]
-        #expect(DriftAlert.compute(from: records) != nil)
+        XCTAssertNotNil(DriftAlert.compute(from: records))
     }
 
-    @Test("No alert if same day and under one hour")
-    func sameDayUnderHour() {
+    func testSameDayUnderHour() {
         let records = [
             record(avg: 4.0, at: 1000),
             record(avg: 5.0, at: 2000)
         ]
-        #expect(DriftAlert.compute(from: records) == nil)
+        XCTAssertNil(DriftAlert.compute(from: records))
     }
 
-    @Test("Alert on distinct days")
-    func distinctDays() {
+    func testDistinctDays() {
         let day1 = record(avg: 4.0, at: 0)
         let day2 = record(avg: 5.0, at: 86400 + 1000)
-        #expect(DriftAlert.compute(from: [day1, day2]) != nil)
+        XCTAssertNotNil(DriftAlert.compute(from: [day1, day2]))
     }
 
-    @Test("Non-poor records do not trigger")
-    func nonPoor() {
+    func testNonPoor() {
         let records = [
             record(avg: 1.0, at: 0),
             record(avg: 1.5, at: 86400)
         ]
-        #expect(DriftAlert.compute(from: records) == nil)
+        XCTAssertNil(DriftAlert.compute(from: records))
     }
 
-    @Test("Non-poor records break the consecutive poor run")
-    func nonPoorBreaksRun() {
+    func testNonPoorBreaksRun() {
         let records = [
             record(avg: 4.0, at: 0),      // poor
             record(avg: 4.5, at: 86400),  // poor, far apart
             record(avg: 1.0, at: 90000),  // good — breaks the run
             record(avg: 4.0, at: 92000)   // poor, recent but close to previous poor
         ]
-        #expect(DriftAlert.compute(from: records) == nil)
+        XCTAssertNil(DriftAlert.compute(from: records))
     }
 
-    @Test("Only the final consecutive poor run is considered")
-    func onlySuffixRun() {
+    func testOnlySuffixRun() {
         let records = [
             record(avg: 4.0, at: 0),     // poor
             record(avg: 4.5, at: 18000), // poor, > 1h from first
@@ -67,26 +59,24 @@ struct DriftAlertTests {
             record(avg: 4.0, at: 25000), // poor
             record(avg: 4.5, at: 26000)  // poor, < 1h and same day
         ]
-        #expect(DriftAlert.compute(from: records) == nil)
+        XCTAssertNil(DriftAlert.compute(from: records))
     }
 
-    @Test("Final consecutive poor run alerts when far apart")
-    func suffixRunAlerts() {
+    func testSuffixRunAlerts() {
         let records = [
             record(avg: 1.0, at: 0),      // good
             record(avg: 4.0, at: 1000),   // poor
             record(avg: 4.5, at: 4600)    // poor, 1h after previous
         ]
-        #expect(DriftAlert.compute(from: records) != nil)
+        XCTAssertNotNil(DriftAlert.compute(from: records))
     }
 
-    @Test("A single final poor record after good records does not alert")
-    func singleFinalPoor() {
+    func testSingleFinalPoor() {
         let records = [
             record(avg: 1.0, at: 0),
             record(avg: 4.0, at: 86400)
         ]
-        #expect(DriftAlert.compute(from: records) == nil)
+        XCTAssertNil(DriftAlert.compute(from: records))
     }
 
     private func record(avg: Double, at offset: TimeInterval) -> VerificationRecord {
diff --git a/Tests/ICCeryCoreTests/FileHelpersTests.swift b/Tests/ICCeryCoreTests/FileHelpersTests.swift
index 0854f8c..32a99a8 100644
--- a/Tests/ICCeryCoreTests/FileHelpersTests.swift
+++ b/Tests/ICCeryCoreTests/FileHelpersTests.swift
@@ -1,4 +1,4 @@
-import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 
@@ -13,91 +13,88 @@ private func touch(_ url: URL, _ contents: String = "x") throws {
     try contents.write(to: url, atomically: true, encoding: .utf8)
 }
 
-@Suite("PathSecurity")
-struct PathSecurityTests {
-    @Test func rejectsTraversalAndSeparators() {
+final class PathSecurityTests: XCTestCase {
+    func testRejectsTraversalAndSeparators() {
         for bad in ["a/b", "a\\b", "..", "a/../b", "", "..x"] {
-            #expect(!PathSecurity.isValidBasename(bad))
-            #expect(throws: PathSecurity.Error.self) {
-                try PathSecurity.sanitizeBasename(bad)
+            XCTAssertFalse(PathSecurity.isValidBasename(bad))
+            XCTAssertThrowsError(try PathSecurity.sanitizeBasename(bad)) { error in
+                XCTAssertTrue(error is PathSecurity.Error)
             }
         }
     }
 
-    @Test func acceptsNormalNames() {
+    func testAcceptsNormalNames() {
         for good in ["target", "My Target 01", "écheneau-ümläut", "a.b"] {
-            #expect(PathSecurity.isValidBasename(good))
+            XCTAssertTrue(PathSecurity.isValidBasename(good))
         }
     }
 
-    @Test func resolveSafeCwdPrefersExplicit() throws {
+    func testResolveSafeCwdPrefersExplicit() throws {
         let dir = try tempDir()
-        #expect(PathSecurity.resolveSafeCwd(dir) == dir)
+        XCTAssertEqual(PathSecurity.resolveSafeCwd(dir), dir)
     }
 
-    @Test func resolveSafeCwdNeverReturnsNil() {
+    func testResolveSafeCwdNeverReturnsNil() {
         let missing = URL(fileURLWithPath: "/nonexistent-\(UUID().uuidString)")
         let resolved = PathSecurity.resolveSafeCwd(missing)
-        #expect(FileManager.default.fileExists(atPath: resolved.path))
+        XCTAssertTrue(FileManager.default.fileExists(atPath: resolved.path))
     }
 }
 
-@Suite("AtomicFileWriter")
-struct AtomicFileWriterTests {
-    @Test func writesAndLeavesNoTmp() throws {
+final class AtomicFileWriterTests: XCTestCase {
+    func testWritesAndLeavesNoTmp() throws {
         let dir = try tempDir()
         let url = dir.appendingPathComponent("state.json")
         try AtomicFileWriter.write(Data("{\"a\":1}".utf8), to: url)
-        #expect(try String(contentsOf: url, encoding: .utf8) == "{\"a\":1}")
-        #expect(!FileManager.default.fileExists(atPath: url.appendingPathExtension("tmp").path))
+        XCTAssertEqual(try String(contentsOf: url, encoding: .utf8), "{\"a\":1}")
+        XCTAssertFalse(FileManager.default.fileExists(atPath: url.appendingPathExtension("tmp").path))
     }
 
-    @Test func overwritesExistingAtomically() throws {
+    func testOverwritesExistingAtomically() throws {
         let dir = try tempDir()
         let url = dir.appendingPathComponent("f.txt")
         try AtomicFileWriter.write("one", to: url)
         try AtomicFileWriter.write("two-longer", to: url)
-        #expect(try String(contentsOf: url, encoding: .utf8) == "two-longer")
+        XCTAssertEqual(try String(contentsOf: url, encoding: .utf8), "two-longer")
     }
 
-    @Test func createsParentDirs() throws {
+    func testCreatesParentDirs() throws {
         let dir = try tempDir()
         let url = dir.appendingPathComponent("a/b/c/deep.json")
         try AtomicFileWriter.write("{}", to: url)
-        #expect(FileManager.default.fileExists(atPath: url.path))
+        XCTAssertTrue(FileManager.default.fileExists(atPath: url.path))
     }
 }
 
-@Suite("ArtefactProbe")
-struct ArtefactProbeTests {
-    @Test func verifyProgression() throws {
+final class ArtefactProbeTests: XCTestCase {
+    func testVerifyProgression() throws {
         let dir = try tempDir()
         var v = ArtefactProbe.verify(basename: "t", cwd: dir)
-        #expect(v == StageArtefacts())
+        XCTAssertEqual(v, StageArtefacts())
 
         try touch(dir.appendingPathComponent("t.ti1"))
         v = ArtefactProbe.verify(basename: "t", cwd: dir)
-        #expect(v.stage1Complete && !v.stage2Complete && !v.stage3Complete)
+        XCTAssertTrue(v.stage1Complete && !v.stage2Complete && !v.stage3Complete)
 
         try touch(dir.appendingPathComponent("t.ti2"))
         try touch(dir.appendingPathComponent("t.ti3"))
         v = ArtefactProbe.verify(basename: "t", cwd: dir)
-        #expect(v.stage2Complete && v.stage3Complete && !v.stage4Complete)
+        XCTAssertTrue(v.stage2Complete && v.stage3Complete && !v.stage4Complete)
 
         try touch(dir.appendingPathComponent("t.icc"))
         v = ArtefactProbe.verify(basename: "t", cwd: dir)
-        #expect(v.stage4Complete && v.profilePath?.pathExtension == "icc")
+        XCTAssertTrue(v.stage4Complete && v.profilePath?.pathExtension == "icc")
     }
 
-    @Test func icmWinsOverIcc() throws {
+    func testIcmWinsOverIcc() throws {
         let dir = try tempDir()
         try touch(dir.appendingPathComponent("p.icc"))
         try touch(dir.appendingPathComponent("p.icm"))
         let profile = ArtefactProbe.resolveProfile(basename: "p", cwd: dir)
-        #expect(profile?.pathExtension == "icm")
+        XCTAssertEqual(profile?.pathExtension, "icm")
     }
 
-    @Test func enumeratesPassesPagesAndCAL() throws {
+    func testEnumeratesPassesPagesAndCAL() throws {
         let dir = try tempDir()
         for name in [
             "t.ti1", "t.ti2", "t.tif", "t.2.tif", "t_03.tif",
@@ -115,15 +112,15 @@ struct ArtefactProbeTests {
             "t.ti3", "t_pass1.ti3", "t_pass2.ti3",
             "t.icc", "t.gam", "CAL_t.ti1", "CAL_t.cal",
         ] {
-            #expect(names.contains(expected), "missing \(expected)")
+            XCTAssertTrue(names.contains(expected), "missing \(expected)")
         }
-        #expect(!names.contains("other.ti1"))
-        #expect(!names.contains("t.txt"))
-        #expect(!names.contains("CAL_other.ti1"))
+        XCTAssertFalse(names.contains("other.ti1"))
+        XCTAssertFalse(names.contains("t.txt"))
+        XCTAssertFalse(names.contains("CAL_other.ti1"))
     }
 
-    @Test func emptyDirReturnsEmpty() throws {
+    func testEmptyDirReturnsEmpty() throws {
         let dir = try tempDir()
-        #expect(ArtefactProbe.existingArtefacts(basename: "x", cwd: dir).isEmpty)
+        XCTAssertTrue(ArtefactProbe.existingArtefacts(basename: "x", cwd: dir).isEmpty)
     }
 }
diff --git a/Tests/ICCeryCoreTests/GamutGeometryBuilderTests.swift b/Tests/ICCeryCoreTests/GamutGeometryBuilderTests.swift
index 5802421..d3f1b31 100644
--- a/Tests/ICCeryCoreTests/GamutGeometryBuilderTests.swift
+++ b/Tests/ICCeryCoreTests/GamutGeometryBuilderTests.swift
@@ -1,15 +1,13 @@
-import Testing
+import XCTest
 import SceneKit
 import ICCeryCore
 @testable import ICCery
 
 /// ``GamutSceneGeometryBuilder`` edge-case tests.
-@Suite("Gamut scene geometry builder")
 @MainActor
-struct GamutGeometryBuilderTests {
+final class GamutGeometryBuilderTests: XCTestCase {
 
-    @Test("Drops out-of-bounds faces from the element without crashing")
-    func dropsOutOfBoundsFaces() {
+    func testDropsOutOfBoundsFaces() {
         let white = GamutVertex(
             lab: LabColor(l: 100, a: 0, b: 0),
             rgb: DisplayRGB(r: 1, g: 1, b: 1)
@@ -28,6 +26,6 @@ struct GamutGeometryBuilderTests {
 
         let (_, element) = GamutSceneGeometryBuilder.geometry(for: mesh)
 
-        #expect(element.primitiveCount == 1, "Only the in-bounds face should be in the index buffer")
+        XCTAssertEqual(element.primitiveCount, 1, "Only the in-bounds face should be in the index buffer")
     }
 }
diff --git a/Tests/ICCeryCoreTests/GamutMeshParserTests.swift b/Tests/ICCeryCoreTests/GamutMeshParserTests.swift
index c3643a2..cb54693 100644
--- a/Tests/ICCeryCoreTests/GamutMeshParserTests.swift
+++ b/Tests/ICCeryCoreTests/GamutMeshParserTests.swift
@@ -1,10 +1,9 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
 /// ``GamutMeshParser`` acceptance + edge-case tests.
-@Suite("Gamut mesh parser")
-struct GamutMeshParserTests {
+final class GamutMeshParserTests: XCTestCase {
 
     /// Returns the bundled real `sRGB.gam` in `Resources/Argyll/reference_gamuts`.
     private var bundledSRGBGamURL: URL {
@@ -13,16 +12,14 @@ struct GamutMeshParserTests {
         return resource.appendingPathComponent("Argyll/reference_gamuts/sRGB.gam")
     }
 
-    @Test("Parses bundled sRGB.gam")
-    func parsesBundledSRGB() throws {
+    func testParsesBundledSRGB() throws {
         let mesh = try GamutMeshParser.parse(url: bundledSRGBGamURL)
 
-        #expect(mesh.vertices.count == 448, "sRGB.gam has 448 vertices")
-        #expect(mesh.faces.count == 892, "sRGB.gam has 892 faces")
+        XCTAssertEqual(mesh.vertices.count, 448, "sRGB.gam has 448 vertices")
+        XCTAssertEqual(mesh.faces.count, 892, "sRGB.gam has 892 faces")
     }
 
-    @Test("Discards VERTEX_NO and uses push-order indices")
-    func discardsVertexNo() throws {
+    func testDiscardsVertexNo() throws {
         let text = """
         GAMUT
         NUMBER_OF_FIELDS 4
@@ -49,14 +46,13 @@ struct GamutMeshParserTests {
 
         let mesh = try GamutMeshParser.parse(text: text)
 
-        #expect(mesh.vertices.count == 4)
-        #expect(mesh.faces.count == 2)
-        #expect(mesh.vertices[0].lab == LabColor(l: 10, a: 20, b: 30))
-        #expect(mesh.vertices[3].lab == LabColor(l: 40, a: 50, b: 60))
+        XCTAssertEqual(mesh.vertices.count, 4)
+        XCTAssertEqual(mesh.faces.count, 2)
+        XCTAssertEqual(mesh.vertices[0].lab, LabColor(l: 10, a: 20, b: 30))
+        XCTAssertEqual(mesh.vertices[3].lab, LabColor(l: 40, a: 50, b: 60))
     }
 
-    @Test("Ignores comments and blank lines")
-    func ignoresComments() throws {
+    func testIgnoresComments() throws {
         let text = """
         # Header comment
         NUMBER_OF_FIELDS 4
@@ -81,12 +77,11 @@ struct GamutMeshParserTests {
         """
 
         let mesh = try GamutMeshParser.parse(text: text)
-        #expect(mesh.vertices.count == 2)
-        #expect(mesh.faces.count == 1)
+        XCTAssertEqual(mesh.vertices.count, 2)
+        XCTAssertEqual(mesh.faces.count, 1)
     }
 
-    @Test("Remaps coordinates to x=a*, y=L*, z=b*")
-    func remapsCoordinates() throws {
+    func testRemapsCoordinates() throws {
         let text = """
         NUMBER_OF_FIELDS 4
         BEGIN_DATA_FORMAT
@@ -99,11 +94,10 @@ struct GamutMeshParserTests {
         """
 
         let mesh = try GamutMeshParser.parse(text: text)
-        #expect(mesh.vertices.first?.position == SIMD3<Float>(-20, 50, 80))
+        XCTAssertEqual(mesh.vertices.first?.position, SIMD3<Float>(-20, 50, 80))
     }
 
-    @Test("Computes per-vertex sRGB colour")
-    func computesVertexColor() throws {
+    func testComputesVertexColor() throws {
         let text = """
         NUMBER_OF_FIELDS 4
         BEGIN_DATA_FORMAT
@@ -116,14 +110,13 @@ struct GamutMeshParserTests {
         """
 
         let mesh = try GamutMeshParser.parse(text: text)
-        let white = try #require(mesh.vertices.first).rgb
-        #expect(white.r > 0.95)
-        #expect(white.g > 0.95)
-        #expect(white.b > 0.95)
+        let white = try XCTUnwrap(mesh.vertices.first).rgb
+        XCTAssertTrue(white.r > 0.95)
+        XCTAssertTrue(white.g > 0.95)
+        XCTAssertTrue(white.b > 0.95)
     }
 
-    @Test("Drops out-of-bounds face indices")
-    func dropsOutOfBoundsFaces() throws {
+    func testDropsOutOfBoundsFaces() throws {
         let text = """
         NUMBER_OF_FIELDS 4
         BEGIN_DATA_FORMAT
@@ -146,21 +139,23 @@ struct GamutMeshParserTests {
         """
 
         let mesh = try GamutMeshParser.parse(text: text)
-        #expect(mesh.faces.count == 1)
+        XCTAssertEqual(mesh.faces.count, 1)
     }
 
-    @Test("Throws on empty file")
-    func throwsOnEmptyFile() {
-        #expect(throws: GamutMeshParseError.noDataBlock) {
-            _ = try GamutMeshParser.parse(text: "")
+    func testThrowsOnEmptyFile() {
+        XCTAssertThrowsError(try GamutMeshParser.parse(text: "")) { error in
+            guard case GamutMeshParseError.noDataBlock = error else {
+                return XCTFail("Expected GamutMeshParseError.noDataBlock, got \(error)")
+            }
         }
     }
 
-    @Test("Throws when file is missing")
-    func throwsWhenMissing() {
+    func testThrowsWhenMissing() {
         let url = URL(fileURLWithPath: "/nonexistent/path/to/mesh.gam")
-        #expect(throws: GamutMeshParseError.missingFile) {
-            _ = try GamutMeshParser.parse(url: url)
+        XCTAssertThrowsError(try GamutMeshParser.parse(url: url)) { error in
+            guard case GamutMeshParseError.missingFile = error else {
+                return XCTFail("Expected GamutMeshParseError.missingFile, got \(error)")
+            }
         }
     }
 }
diff --git a/Tests/ICCeryCoreTests/IccgamutArgsTests.swift b/Tests/ICCeryCoreTests/IccgamutArgsTests.swift
index 2ef2ba9..86916a9 100644
--- a/Tests/ICCeryCoreTests/IccgamutArgsTests.swift
+++ b/Tests/ICCeryCoreTests/IccgamutArgsTests.swift
@@ -1,16 +1,14 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("IccgamutArgs")
-struct IccgamutArgsTests {
+final class IccgamutArgsTests: XCTestCase {
 
-    @Test("Density is 10 and not a directory")
-    func densityNotDirectory() throws {
+    func testDensityNotDirectory() throws {
         let config = IccgamutConfig(
             profileURL: URL(fileURLWithPath: "/tmp/MyProfile.icc")
         )
         let args = try IccgamutArgs.build(config: config)
-        #expect(args == ["-v", "-d", "10", "/tmp/MyProfile.icc"])
+        XCTAssertEqual(args, ["-v", "-d", "10", "/tmp/MyProfile.icc"])
     }
 }
diff --git a/Tests/ICCeryCoreTests/LpArgsTests.swift b/Tests/ICCeryCoreTests/LpArgsTests.swift
index 4dcb22a..893aa96 100644
--- a/Tests/ICCeryCoreTests/LpArgsTests.swift
+++ b/Tests/ICCeryCoreTests/LpArgsTests.swift
@@ -1,12 +1,11 @@
-import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 
 /// Issue 15 — `lp` argv goldens (docs/11 `build_lp_args`).
 /// `-d`/`options`/`-t` handling is in `CupsService`; these tests cover
 /// flag order, captured-option precedence, and sanitisation.
-@Suite("LpArgs")
-struct LpArgsTests {
+final class LpArgsTests: XCTestCase {
 
     private let tiff = "/tmp/work/target_001.tif"
     private let queue = "EPSON_XP_55_Series"
@@ -20,112 +19,100 @@ struct LpArgsTests {
             options: options, optionKeys: optionKeys)
     }
 
-    @Test("Header: -d queue -t title, both AP_* first, TIFF last")
-    func header() throws {
+    func testHeader() throws {
         let argv = try build()
-        #expect(Array(argv[0...1]) == ["-d", queue])
-        #expect(Array(argv[2...3]) == ["-t", "ICCery Target - target_001.tif"])
-        #expect(Array(argv[4...5])
-            == ["-o", "AP_ColorMatchingMode=AP_ApplicationColorMatching"])
-        #expect(Array(argv[6...7])
-            == ["-o", "AP.ColorMatchingMode=AP_ApplicationColorMatching"])
-        #expect(argv.last == tiff)
-        #expect(!argv.contains { $0 == "raw" || $0 == "-o raw" })
+        XCTAssertEqual(Array(argv[0...1]), ["-d", queue])
+        XCTAssertEqual(Array(argv[2...3]), ["-t", "ICCery Target - target_001.tif"])
+        XCTAssertEqual(Array(argv[4...5]), ["-o", "AP_ColorMatchingMode=AP_ApplicationColorMatching"])
+        XCTAssertEqual(Array(argv[6...7]), ["-o", "AP.ColorMatchingMode=AP_ApplicationColorMatching"])
+        XCTAssertEqual(argv.last, tiff)
+        XCTAssertFalse(argv.contains { $0 == "raw" || $0 == "-o raw" })
     }
 
-    @Test("Never emits -o raw; captured raw= is dropped")
-    func neverRaw() throws {
+    func testNeverRaw() throws {
         let argv = try build(options: PrintOptions(
             cupsOptions: "raw=true MediaType=Photo"))
         for (i, arg) in argv.enumerated() where arg == "-o" {
-            #expect(argv[i + 1] != "raw")
-            #expect(argv[i + 1] != "raw=true")
+            XCTAssertNotEqual(argv[i + 1], "raw")
+            XCTAssertNotEqual(argv[i + 1], "raw=true")
         }
-        #expect(!argv.contains { $0.hasPrefix("raw=") })
-        #expect(argv.contains("MediaType=Photo"))
+        XCTAssertFalse(argv.contains { $0.hasPrefix("raw=") })
+        XCTAssertTrue(argv.contains("MediaType=Photo"))
     }
 
-    @Test("Captured options replayed after AP_* headers")
-    func capturedReplay() throws {
+    func testCapturedReplay() throws {
         let argv = try build(options: PrintOptions(
             cupsOptions: "InputSlot=Rear MediaType=Photo"))
         let rear = argv.firstIndex(of: "InputSlot=Rear")!
         let apFirst = argv.firstIndex(of:
             "AP_ColorMatchingMode=AP_ApplicationColorMatching")!
-        #expect(rear > apFirst)
+        XCTAssertTrue(rear > apFirst)
     }
 
-    @Test("Captured wins: media key present → derived media skipped")
-    func capturedWinsMedia() throws {
+    func testCapturedWinsMedia() throws {
         let argv = try build(
             options: PrintOptions(
                 mediaType: "Plain",
                 cupsOptions: "MediaType=Glossy"),
             optionKeys: ["MediaType"])
-        #expect(argv.contains("MediaType=Glossy"))
-        #expect(!argv.contains("MediaType=Plain"))
+        XCTAssertTrue(argv.contains("MediaType=Glossy"))
+        XCTAssertFalse(argv.contains("MediaType=Plain"))
     }
 
-    @Test("Media emitted via detected key when not captured")
-    func mediaDerived() throws {
+    func testMediaDerived() throws {
         let argv = try build(
             options: PrintOptions(mediaType: "SemiGloss"),
             optionKeys: ["CNIJMediaType", "MediaType"])
         // CNIJMediaType wins over MediaType in detection order.
-        #expect(argv.contains("CNIJMediaType=SemiGloss"))
-        #expect(!argv.contains("MediaType=SemiGloss"))
+        XCTAssertTrue(argv.contains("CNIJMediaType=SemiGloss"))
+        XCTAssertFalse(argv.contains("MediaType=SemiGloss"))
     }
 
-    @Test("Driver bypass emitted when absent, skipped when captured")
-    func bypassRules() throws {
+    func testBypassRules() throws {
         let withBypass = try build(
             optionKeys: ["EPIJ_CMat"])
-        #expect(withBypass.contains("EPIJ_CMat=3"))
+        XCTAssertTrue(withBypass.contains("EPIJ_CMat=3"))
 
         let captured = try build(
             options: PrintOptions(cupsOptions: "EPIJ_CMat=1"),
             optionKeys: ["EPIJ_CMat"])
         // Captured value kept, detection not re-applied.
-        #expect(captured.filter { $0.hasPrefix("EPIJ_CMat") }
-            == ["EPIJ_CMat=1"])
+        XCTAssertEqual(captured.filter { $0.hasPrefix("EPIJ_CMat") }, ["EPIJ_CMat=1"])
     }
 
-    @Test("Orientation: portrait=3 landscape=4; captured wins")
-    func orientation() throws {
-        #expect(try build(options: PrintOptions(orientation: "portrait"))
+    func testOrientation() throws {
+        XCTAssertTrue(try build(options: PrintOptions(orientation: "portrait"))
             .contains("orientation-requested=3"))
-        #expect(try build(options: PrintOptions(orientation: "landscape"))
+        XCTAssertTrue(try build(options: PrintOptions(orientation: "landscape"))
             .contains("orientation-requested=4"))
         let capturedOrients = try build(options: PrintOptions(
             orientation: "landscape",
             cupsOptions: "orientation-requested=5"))
-        #expect(!capturedOrients.contains("orientation-requested=4"))
-        #expect(capturedOrients.contains("orientation-requested=5"))
+        XCTAssertFalse(capturedOrients.contains("orientation-requested=4"))
+        XCTAssertTrue(capturedOrients.contains("orientation-requested=5"))
     }
 
-    @Test("PageSize emitted unless captured")
-    func pageSize() throws {
-        #expect(try build(options: PrintOptions(paperSize: "A4"))
+    func testPageSize() throws {
+        XCTAssertTrue(try build(options: PrintOptions(paperSize: "A4"))
             .contains("PageSize=A4"))
         let capturedSize = try build(options: PrintOptions(
             paperSize: "A4", cupsOptions: "PageSize=Letter"))
-        #expect(!capturedSize.contains("PageSize=A4"))
-        #expect(capturedSize.contains("PageSize=Letter"))
+        XCTAssertFalse(capturedSize.contains("PageSize=A4"))
+        XCTAssertTrue(capturedSize.contains("PageSize=Letter"))
     }
 
-    @Test("Sanitise rejects `;`, newline, and shell metachars")
-    func sanitise() throws {
-        #expect(throws: LpArgsError.self) {
-            _ = try build(options: PrintOptions(
-                cupsOptions: "InputSlot=Rear;rm -rf /"))
+    func testSanitise() throws {
+        XCTAssertThrowsError(try build(options: PrintOptions(
+            cupsOptions: "InputSlot=Rear;rm -rf /"))) { error in
+            XCTAssertTrue(error is LpArgsError)
         }
-        #expect(throws: LpArgsError.self) {
-            _ = try build(options: PrintOptions(
-                cupsOptions: "InputSlot=Rear\nMediaType=Photo"))
+        XCTAssertThrowsError(try build(options: PrintOptions(
+            cupsOptions: "InputSlot=Rear\nMediaType=Photo"))) { error in
+            XCTAssertTrue(error is LpArgsError)
         }
-        #expect(throws: LpArgsError.self) {
-            _ = try build(options: PrintOptions(
-                cupsOptions: "InputSlot=$(whoami)"))
+        XCTAssertThrowsError(try build(options: PrintOptions(
+            cupsOptions: "InputSlot=$(whoami)"))) { error in
+            XCTAssertTrue(error is LpArgsError)
         }
     }
 }
diff --git a/Tests/ICCeryCoreTests/MeasurementTests.swift b/Tests/ICCeryCoreTests/MeasurementTests.swift
index 3687237..aac8cdb 100644
--- a/Tests/ICCeryCoreTests/MeasurementTests.swift
+++ b/Tests/ICCeryCoreTests/MeasurementTests.swift
@@ -1,12 +1,10 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("InstrumentParser")
-struct InstrumentParserTests {
+final class InstrumentParserTests: XCTestCase {
 
-    @Test("Parses pretty-printed instlist JSON")
-    func json() throws {
+    func testJson() throws {
         let json = """
         {
           "event": "instruments",
@@ -18,134 +16,118 @@ struct InstrumentParserTests {
         }
         """
         let devices = try InstrumentParser.parse(json)
-        #expect(devices.count == 3)
-        #expect(devices[0].port == 1)
-        #expect(devices[0].name == "X-Rite i1Pro")
-        #expect(devices[2].port == 3)
+        XCTAssertEqual(devices.count, 3)
+        XCTAssertEqual(devices[0].port, 1)
+        XCTAssertEqual(devices[0].name, "X-Rite i1Pro")
+        XCTAssertEqual(devices[2].port, 3)
     }
 
-    @Test("Falls back to regex for legacy instlist text")
-    func regexFallback() throws {
+    func testRegexFallback() throws {
         let text = """
         1: 'X-Rite i1Pro' on usb
         2: 'ColorMunki Smile'
         """ + "\n"
         let devices = try InstrumentParser.parse(text)
-        #expect(devices.count == 2)
-        #expect(devices[0].port == 1)
-        #expect(devices[1].name == "ColorMunki Smile")
+        XCTAssertEqual(devices.count, 2)
+        XCTAssertEqual(devices[0].port, 1)
+        XCTAssertEqual(devices[1].name, "ColorMunki Smile")
     }
 
-    @Test("Empty output returns no devices")
-    func empty() throws {
-        #expect(try InstrumentParser.parse("").isEmpty)
+    func testEmpty() throws {
+        XCTAssertTrue(try InstrumentParser.parse("").isEmpty)
     }
 }
 
-@Suite("ChartreadArgs")
-struct ChartreadArgsTests {
+final class ChartreadArgsTests: XCTestCase {
 
-    @Test("Baseline argv and port 1 omits -c")
-    func baseline() throws {
+    func testBaseline() throws {
         let config = ChartreadConfig(basename: "target", selectedPort: 1)
         let args = try ChartreadArgs.build(config: config)
-        #expect(args == ["-v", "-u", "target"])
+        XCTAssertEqual(args, ["-v", "-u", "target"])
     }
 
-    @Test("Port > 1 emits -c")
-    func portArgument() throws {
+    func testPortArgument() throws {
         let config = ChartreadConfig(basename: "target", selectedPort: 3)
         let args = try ChartreadArgs.build(config: config)
-        #expect(args == ["-v", "-u", "-c", "3", "target"])
+        XCTAssertEqual(args, ["-v", "-u", "-c", "3", "target"])
     }
 
-    @Test("LEDs emit -Y l")
-    func leds() throws {
+    func testLeds() throws {
         let config = ChartreadConfig(
             basename: "target",
             selectedPort: 2,
             enableLEDs: true
         )
         let args = try ChartreadArgs.build(config: config)
-        #expect(args.contains("-Y"))
-        #expect(args.contains("l"))
+        XCTAssertTrue(args.contains("-Y"))
+        XCTAssertTrue(args.contains("l"))
     }
 
-    @Test("Auto omits -c")
-    func autoPort() throws {
+    func testAutoPort() throws {
         let config = ChartreadConfig(basename: "target")
         let args = try ChartreadArgs.build(config: config)
-        #expect(!args.contains("-c"))
+        XCTAssertFalse(args.contains("-c"))
     }
 }
 
-@Suite("ChartreadClassifier")
-struct ChartreadClassifierTests {
+final class ChartreadClassifierTests: XCTestCase {
 
-    @Test("Calibration prompt")
-    func calibration() {
+    func testCalibration() {
         let r = ChartreadClassifier.classify(
             line: "Place instrument on calibration tile and hit [Space] to calibrate.",
             previousState: .idle
         )
-        #expect(r.state == .calibrating)
+        XCTAssertEqual(r.state, .calibrating)
     }
 
-    @Test("Strip awaiting")
-    func awaitingStrip() {
+    func testAwaitingStrip() {
         let r = ChartreadClassifier.classify(
             line: "Hit [Space] to read strip A",
             previousState: .calibrating
         )
-        #expect(r.state == .awaitingStrip)
+        XCTAssertEqual(r.state, .awaitingStrip)
     }
 
-    @Test("Done prompt")
-    func done() {
+    func testDone() {
         let r = ChartreadClassifier.classify(
             line: "'d' if/when done",
             previousState: .awaitingStrip
         )
-        #expect(r.state == .allStripsRead)
+        XCTAssertEqual(r.state, .allStripsRead)
     }
 
-    @Test("XY place sheet")
-    func placeSheet() {
+    func testPlaceSheet() {
         let r = ChartreadClassifier.classify(
             line: "Please place sheet 1 of 2 on the table",
             previousState: .idle
         )
-        #expect(r.state == .tablePlaceSheet)
-        #expect(r.sheetNumber == 1)
-        #expect(r.sheetTotal == 2)
+        XCTAssertEqual(r.state, .tablePlaceSheet)
+        XCTAssertEqual(r.sheetNumber, 1)
+        XCTAssertEqual(r.sheetTotal, 2)
     }
 
-    @Test("XY locate patch")
-    func locatePatch() {
+    func testLocatePatch() {
         let r = ChartreadClassifier.classify(
             line: "locate patch A1 with the sight,",
             previousState: .tablePlaceSheet
         )
-        #expect(r.state == .tableAlign)
-        #expect(r.alignmentPatch == "A1")
+        XCTAssertEqual(r.state, .tableAlign)
+        XCTAssertEqual(r.alignmentPatch, "A1")
     }
 
-    @Test("Remove sheet notice preserves state")
-    func removeNotice() {
+    func testRemoveNotice() {
         let r = ChartreadClassifier.classify(
             line: "Please remove last sheet from table",
             previousState: .tablePlaceSheet
         )
-        #expect(r.state == .tablePlaceSheet)
-        #expect(r.isRemoveSheetNotice == true)
+        XCTAssertEqual(r.state, .tablePlaceSheet)
+        XCTAssertEqual(r.isRemoveSheetNotice, true)
     }
 }
 
-@Suite("ChartreadRow")
-struct ChartreadRowTests {
+final class ChartreadRowTests: XCTestCase {
 
-    @Test("Decodes row JSON")
-    func decode() throws {
+    func testDecode() throws {
         let json = """
         {"event": "row_complete", "row_id": "A", "row_index": 0, "total_rows": 2,
          "patch_count": 1, "patches": [
@@ -155,13 +137,12 @@ struct ChartreadRowTests {
          ]}
         """
         let row = try JSONDecoder().decode(ChartreadRow.self, from: Data(json.utf8))
-        #expect(row.rowId == "A")
-        #expect(row.patchCount == 1)
-        #expect(row.patches[0].measured.lab?.l == 51)
+        XCTAssertEqual(row.rowId, "A")
+        XCTAssertEqual(row.patchCount, 1)
+        XCTAssertEqual(row.patches[0].measured.lab?.l, 51)
     }
 
-    @Test("Decodes a row carrying both XYZ and Lab arrays")
-    func decodeXYZAndLab() throws {
+    func testDecodeXYZAndLab() throws {
         let json = """
         {"event": "row_complete", "row_id": "B", "row_index": 1, "total_rows": 2,
          "patch_count": 1, "patches": [
@@ -171,88 +152,78 @@ struct ChartreadRowTests {
         """
         let row = try JSONDecoder().decode(ChartreadRow.self, from: Data(json.utf8))
         let measured = row.patches[0].measured
-        #expect(measured.xyz == CIEXYZ(x: 30.5, y: 32.1, z: 25.9))
-        #expect(measured.lab == CIELab(l: 63.4, a: 2.5, b: -8.2))
+        XCTAssertEqual(measured.xyz, CIEXYZ(x: 30.5, y: 32.1, z: 25.9))
+        XCTAssertEqual(measured.lab, CIELab(l: 63.4, a: 2.5, b: -8.2))
     }
 
-    @Test("XYZColor/CIEXYZ encode as an unkeyed three-number array")
-    func xyzWireEncoding() throws {
+    func testXyzWireEncoding() throws {
         for color in [XYZColor(x: 1.5, y: 2.5, z: 3.5), CIEXYZ(x: 1.5, y: 2.5, z: 3.5)] {
             let value = try JSONSerialization.jsonObject(
                 with: JSONEncoder().encode(color))
-            #expect(value as? [Double] == [1.5, 2.5, 3.5])
+            XCTAssertEqual(value as? [Double], [1.5, 2.5, 3.5])
         }
     }
 
-    @Test("LabColor/CIELab encode as an unkeyed three-number array")
-    func labWireEncoding() throws {
+    func testLabWireEncoding() throws {
         for color in [LabColor(l: 50, a: -1, b: 2), CIELab(l: 50, a: -1, b: 2)] {
             let value = try JSONSerialization.jsonObject(
                 with: JSONEncoder().encode(color))
-            #expect(value as? [Double] == [50, -1, 2])
+            XCTAssertEqual(value as? [Double], [50, -1, 2])
         }
     }
 
-    @Test("PatchColor keeps the XYZ and Lab keys over unkeyed arrays")
-    func patchColorKeys() throws {
+    func testPatchColorKeys() throws {
         let color = PatchColor(
             xyz: CIEXYZ(x: 10, y: 20, z: 30),
             lab: CIELab(l: 55, a: 1, b: -2))
         let object = try JSONSerialization.jsonObject(
             with: JSONEncoder().encode(color)) as? [String: Any]
-        #expect(object?["XYZ"] as? [Double] == [10, 20, 30])
-        #expect(object?["Lab"] as? [Double] == [55, 1, -2])
-        #expect(object?["spectral"] == nil)
+        XCTAssertEqual(object?["XYZ"] as? [Double], [10, 20, 30])
+        XCTAssertEqual(object?["Lab"] as? [Double], [55, 1, -2])
+        XCTAssertNil(object?["spectral"])
     }
 }
 
-@Suite("ColourMath")
-struct ColourMathTests {
+final class ColourMathTests: XCTestCase {
 
-    @Test("White XYZ to Lab")
-    func whiteLab() {
+    func testWhiteLab() {
         let white = XYZColor(x: 96.4212, y: 100.0, z: 82.5188)
         let lab = LabColorMath.xyzToLab(white)
-        #expect(abs(lab.l - 100) < 0.5)
-        #expect(abs(lab.a) < 0.5)
-        #expect(abs(lab.b) < 0.5)
+        XCTAssertTrue(abs(lab.l - 100) < 0.5)
+        XCTAssertTrue(abs(lab.a) < 0.5)
+        XCTAssertTrue(abs(lab.b) < 0.5)
     }
 
-    @Test("Lab to sRGB roundtrip is clamped")
-    func labToSRGB() {
+    func testLabToSRGB() {
         let red = LabColor(l: 55, a: 80, b: 70)
         let rgb = LabColorMath.labToSRGB(red)
-        #expect(rgb.r > 0.8)
-        #expect(rgb.g < 0.2)
-        #expect(rgb.b < 0.2)
+        XCTAssertTrue(rgb.r > 0.8)
+        XCTAssertTrue(rgb.g < 0.2)
+        XCTAssertTrue(rgb.b < 0.2)
     }
 
-    @Test("Pad white returns DisplayRGB")
-    func padWhite() {
+    func testPadWhite() {
         let white = LabColor(l: 95, a: 0, b: 0)
         let rgb = LabColorMath.labToSRGB(white)
-        #expect(rgb.r > 0.9)
-        #expect(rgb.g > 0.9)
-        #expect(rgb.b > 0.9)
+        XCTAssertTrue(rgb.r > 0.9)
+        XCTAssertTrue(rgb.g > 0.9)
+        XCTAssertTrue(rgb.b > 0.9)
     }
 
-    @Test("Standard CIEDE2000 vector (Sharma)")
-    func ciede2000() {
+    func testCiede2000() {
         let a = LabColor(l: 50, a: -1.3802, b: -84.2814)
         let b = LabColor(l: 50, a: 0.0000, b: -82.7485)
-        #expect(abs(ColorDifference.deltaE00(a, b) - 1.00) < 0.001)
+        XCTAssertTrue(abs(ColorDifference.deltaE00(a, b) - 1.00) < 0.001)
     }
 
-    @Test("Classification respects thresholds")
-    func classify() {
-        #expect(ColorDifference.classify(deltaE: 0.5, goodMax: 2.0, warningMax: 5.0) == .good)
-        #expect(ColorDifference.classify(deltaE: 3.0, goodMax: 2.0, warningMax: 5.0) == .warning)
-        #expect(ColorDifference.classify(deltaE: 6.0, goodMax: 2.0, warningMax: 5.0) == .bad)
+    func testClassify() {
+        XCTAssertEqual(ColorDifference.classify(deltaE: 0.5, goodMax: 2.0, warningMax: 5.0), .good)
+        XCTAssertEqual(ColorDifference.classify(deltaE: 3.0, goodMax: 2.0, warningMax: 5.0), .warning)
+        XCTAssertEqual(ColorDifference.classify(deltaE: 6.0, goodMax: 2.0, warningMax: 5.0), .bad)
     }
 }
 
-@Suite("MeasurementArtefacts")
-struct MeasurementArtefactTests {
+final class MeasurementArtefactTests: XCTestCase {
 
     private func makeCwd() throws -> URL {
         let url = FileManager.default.temporaryDirectory
@@ -261,8 +232,7 @@ struct MeasurementArtefactTests {
         return url
     }
 
-    @Test("Discovers passes in order")
-    func discovery() throws {
+    func testDiscovery() throws {
         let cwd = try makeCwd()
         defer { try? FileManager.default.removeItem(at: cwd) }
 
@@ -271,11 +241,10 @@ struct MeasurementArtefactTests {
         try "C".write(to: cwd.appendingPathComponent("target_pass10.ti3"), atomically: true, encoding: .utf8)
 
         let passes = MeasurementArtefacts.passSnapshots(basename: "target", cwd: cwd)
-        #expect(passes.map(\.lastPathComponent) == ["target_pass1.ti3", "target_pass3.ti3", "target_pass10.ti3"])
+        XCTAssertEqual(passes.map(\.lastPathComponent), ["target_pass1.ti3", "target_pass3.ti3", "target_pass10.ti3"])
     }
 
-    @Test("Snapshot and promote are atomic")
-    func snapshotPromote() throws {
+    func testSnapshotPromote() throws {
         let cwd = try makeCwd()
         defer { try? FileManager.default.removeItem(at: cwd) }
 
@@ -283,16 +252,15 @@ struct MeasurementArtefactTests {
         try "canonical".write(to: canonical, atomically: true, encoding: .utf8)
 
         let pass = try MeasurementArtefacts.snapshotPass(basename: "target", cwd: cwd)
-        #expect(pass.lastPathComponent == "target_pass1.ti3")
-        #expect(!FileManager.default.fileExists(atPath: canonical.path))
+        XCTAssertEqual(pass.lastPathComponent, "target_pass1.ti3")
+        XCTAssertFalse(FileManager.default.fileExists(atPath: canonical.path))
 
         let promoted = try MeasurementArtefacts.promotePass(pass: pass, basename: "target", cwd: cwd)
-        #expect(promoted.lastPathComponent == "target.ti3")
-        #expect(FileManager.default.fileExists(atPath: promoted.path))
+        XCTAssertEqual(promoted.lastPathComponent, "target.ti3")
+        XCTAssertTrue(FileManager.default.fileExists(atPath: promoted.path))
     }
 
-    @Test("Pass collisions handled")
-    func collision() throws {
+    func testCollision() throws {
         let cwd = try makeCwd()
         defer { try? FileManager.default.removeItem(at: cwd) }
 
@@ -302,28 +270,25 @@ struct MeasurementArtefactTests {
 
         try "v2".write(to: canonical, atomically: true, encoding: .utf8)
         let pass2 = try MeasurementArtefacts.snapshotPass(basename: "target", cwd: cwd)
-        #expect(pass2.lastPathComponent == "target_pass2.ti3")
+        XCTAssertEqual(pass2.lastPathComponent, "target_pass2.ti3")
     }
 }
 
-@Suite("AverageArgs")
-struct AverageArgsTests {
+final class AverageArgsTests: XCTestCase {
 
-    @Test("Requires at least two pass files")
-    func passCount() {
+    func testPassCount() {
         let cwd = URL(fileURLWithPath: "/tmp")
         let config = AverageConfig(
             workingDirectory: cwd,
             basename: "target",
             passFiles: [URL(fileURLWithPath: "target_pass1.ti3")]
         )
-        #expect(throws: AverageArgError.self) {
-            _ = try AverageArgs.build(config: config)
+        XCTAssertThrowsError(try AverageArgs.build(config: config)) { error in
+            XCTAssertTrue(error is AverageArgError)
         }
     }
 
-    @Test("Output is last and inputs are relative")
-    func ordering() throws {
+    func testOrdering() throws {
         let cwd = URL(fileURLWithPath: "/tmp")
         let config = AverageConfig(
             workingDirectory: cwd,
@@ -334,8 +299,8 @@ struct AverageArgsTests {
             ]
         )
         let args = try AverageArgs.build(config: config)
-        #expect(args.first == "-v")
-        #expect(args.last == "target.ti3")
-        #expect(args == ["-v", "target_pass1.ti3", "target_pass2.ti3", "target.ti3"])
+        XCTAssertEqual(args.first, "-v")
+        XCTAssertEqual(args.last, "target.ti3")
+        XCTAssertEqual(args, ["-v", "target_pass1.ti3", "target_pass2.ti3", "target.ti3"])
     }
 }
diff --git a/Tests/ICCeryCoreTests/PrintcalArgsTests.swift b/Tests/ICCeryCoreTests/PrintcalArgsTests.swift
index 57caf9e..cd56634 100644
--- a/Tests/ICCeryCoreTests/PrintcalArgsTests.swift
+++ b/Tests/ICCeryCoreTests/PrintcalArgsTests.swift
@@ -1,24 +1,21 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("PrintcalArgs")
-struct PrintcalArgsTests {
+final class PrintcalArgsTests: XCTestCase {
 
     private let tmp = URL(fileURLWithPath: "/tmp/out.cal")
 
-    @Test("Default printcal argv")
-    func defaults() throws {
+    func testDefaults() throws {
         let config = PrintcalConfig(
             ti3Basename: "CAL_demo",
             outputURL: tmp
         )
         let args = try PrintcalArgs.build(config: config)
-        #expect(args == ["-v", "-e", "-o", "/tmp/out.cal", "CAL_demo"])
+        XCTAssertEqual(args, ["-v", "-e", "-o", "/tmp/out.cal", "CAL_demo"])
     }
 
-    @Test("All options and channel limits")
-    func allOptions() throws {
+    func testAllOptions() throws {
         let config = PrintcalConfig(
             ti3Basename: "demo",
             outputURL: tmp,
@@ -32,7 +29,7 @@ struct PrintcalArgsTests {
             ]
         )
         let args = try PrintcalArgs.build(config: config)
-        #expect(args == [
+        XCTAssertEqual(args, [
             "-v", "-e",
             "-I", "-z",
             "-a", "/tmp/old.cal",
@@ -44,39 +41,34 @@ struct PrintcalArgsTests {
         ])
     }
 
-    @Test("Whitespace-only previous calibration path emits no -a")
-    func whitespacePreviousCal() throws {
+    func testWhitespacePreviousCal() throws {
         let config = PrintcalConfig(
             ti3Basename: "demo",
             outputURL: tmp,
             previousCalPath: "   \n\t "
         )
         let args = try PrintcalArgs.build(config: config)
-        #expect(!args.contains("-a"))
-        #expect(args == ["-v", "-e", "-o", "/tmp/out.cal", "CAL_demo"])
+        XCTAssertFalse(args.contains("-a"))
+        XCTAssertEqual(args, ["-v", "-e", "-o", "/tmp/out.cal", "CAL_demo"])
     }
 
-    @Test("Previous calibration path is trimmed before emission")
-    func previousCalTrimmed() throws {
+    func testPreviousCalTrimmed() throws {
         let config = PrintcalConfig(
             ti3Basename: "demo",
             outputURL: tmp,
             previousCalPath: "  /tmp/old.cal  "
         )
         let args = try PrintcalArgs.build(config: config)
-        #expect(args[args.firstIndex(of: "-a")! + 1] == "/tmp/old.cal")
+        XCTAssertEqual(args[args.firstIndex(of: "-a")! + 1], "/tmp/old.cal")
     }
 
-    @Test("Rejects invalid per-channel limit")
-    func rejectsBadChannelLimit() {
+    func testRejectsBadChannelLimit() {
         let config = PrintcalConfig(
             ti3Basename: "demo",
             outputURL: tmp,
             channelLimits: [PrintcalChannelLimit(channel: "K", percent: 150)]
         )
-        #expect(throws: (any Error).self) {
-            _ = try PrintcalArgs.build(config: config)
-        }
+        XCTAssertThrowsError(try PrintcalArgs.build(config: config))
     }
 
 }
diff --git a/Tests/ICCeryCoreTests/PrinttargTests.swift b/Tests/ICCeryCoreTests/PrinttargTests.swift
index bab9fdc..b147afb 100644
--- a/Tests/ICCeryCoreTests/PrinttargTests.swift
+++ b/Tests/ICCeryCoreTests/PrinttargTests.swift
@@ -1,9 +1,9 @@
 import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 
-@Suite("PrinttargArgs")
-struct PrinttargArgsTests {
+final class PrinttargArgsTests: XCTestCase {
 
     private func config(
         instrument: PrintInstrument = .i1,
@@ -28,136 +28,121 @@ struct PrinttargArgsTests {
         )
     }
 
-    @Test("Baseline: -v -u -i i1 -p A4 -R 1 -t 300")
-    func baseline() throws {
+    func testBaseline() throws {
         let args = try PrinttargArgs.build(config: config())
-        #expect(args == ["-v", "-u", "-i", "i1", "-p", "A4",
+        XCTAssertEqual(args, ["-v", "-u", "-i", "i1", "-p", "A4",
                          "-R", "1", "-t", "300", "target"])
     }
 
-    @Test("Default layout is deterministic -R 1, never bare")
-    func deterministicDefault() throws {
+    func testDeterministicDefault() throws {
         let args = try PrinttargArgs.build(config: config())
-        #expect(args.contains("-R"))
-        #expect(!args.contains("-r"))
-        #expect(args[args.firstIndex(of: "-R")! + 1] == "1")
+        XCTAssertTrue(args.contains("-R"))
+        XCTAssertFalse(args.contains("-r"))
+        XCTAssertEqual(args[args.firstIndex(of: "-R")! + 1], "1")
     }
 
-    @Test("Custom seed -R N; seed < 1 throws")
-    func customSeed() throws {
+    func testCustomSeed() throws {
         let args = try PrinttargArgs.build(config: config(layout: .customSeed, seed: 42))
-        #expect(args[args.firstIndex(of: "-R")! + 1] == "42")
-        #expect(throws: PrinttargArgError.self) {
-            try PrinttargArgs.build(config: config(layout: .customSeed, seed: 0))
+        XCTAssertEqual(args[args.firstIndex(of: "-R")! + 1], "42")
+        XCTAssertThrowsError(try PrinttargArgs.build(config: config(layout: .customSeed, seed: 0))) { error in
+            XCTAssertTrue(error is PrinttargArgError)
         }
     }
 
-    @Test("Raster emits -r and supersedes seed (printtarg -r, not targen -r)")
-    func raster() throws {
+    func testRaster() throws {
         let args = try PrinttargArgs.build(config: config(layout: .raster, seed: 9))
-        #expect(args.contains("-r"))
-        #expect(!args.contains("-R"))
+        XCTAssertTrue(args.contains("-r"))
+        XCTAssertFalse(args.contains("-R"))
     }
 
-    @Test("Label: -d emits the resolved string, not a colour space")
-    func label() throws {
+    func testLabel() throws {
         let args = try PrinttargArgs.build(
             config: config(label: "ICCery - t - P - I - D - A - 01/02/2026 03:04"))
         let i = args.firstIndex(of: "-d")!
-        #expect(args[i + 1].hasPrefix("ICCery - t"))
+        XCTAssertTrue(args[i + 1].hasPrefix("ICCery - t"))
     }
 
-    @Test("Bit depth: -t 8-bit, -T 16-bit; DPI range 72-600")
-    func bitDepthAndDPI() throws {
-        #expect(try PrinttargArgs.build(config: config(bitDepth: .sixteen, dpi: 600))
+    func testBitDepthAndDPI() throws {
+        XCTAssertTrue(try PrinttargArgs.build(config: config(bitDepth: .sixteen, dpi: 600))
             .contains("-T"))
-        #expect(try PrinttargArgs.build(config: config(bitDepth: .eight, dpi: 72))
+        XCTAssertTrue(try PrinttargArgs.build(config: config(bitDepth: .eight, dpi: 72))
             .contains("-t"))
-        #expect(throws: PrinttargArgError.self) {
-            try PrinttargArgs.build(config: config(dpi: 71))
+        XCTAssertThrowsError(try PrinttargArgs.build(config: config(dpi: 71))) { error in
+            XCTAssertTrue(error is PrinttargArgError)
         }
-        #expect(throws: PrinttargArgError.self) {
-            try PrinttargArgs.build(config: config(dpi: 601))
+        XCTAssertThrowsError(try PrinttargArgs.build(config: config(dpi: 601))) { error in
+            XCTAssertTrue(error is PrinttargArgError)
         }
     }
 
-    @Test("All instruments emit their Argyll code")
-    func instruments() throws {
+    func testInstruments() throws {
         let expected: [(PrintInstrument, String)] = [
             (.i1, "i1"), (.p3, "p3"), (.cm, "CM"), (.ss, "SS"),
             (.dtp20, "20"), (.dtp22, "22"), (.dtp41, "41"), (.dtp51, "51"),
         ]
         for (inst, code) in expected {
             let args = try PrinttargArgs.build(config: config(instrument: inst))
-            #expect(args[args.firstIndex(of: "-i")! + 1] == code)
+            XCTAssertEqual(args[args.firstIndex(of: "-i")! + 1], code)
         }
     }
 
-    @Test("All fixed page sizes; custom emits WxH in mm")
-    func pageSizes() throws {
+    func testPageSizes() throws {
         for size in PageSize.allCases where size != .custom {
             let args = try PrinttargArgs.build(config: config(pageSize: size))
-            #expect(args[args.firstIndex(of: "-p")! + 1] == size.rawValue)
+            XCTAssertEqual(args[args.firstIndex(of: "-p")! + 1], size.rawValue)
         }
         let custom = try PrinttargArgs.build(config: config(
             pageSize: .custom, customW: 150, customH: 220))
-        #expect(custom[custom.firstIndex(of: "-p")! + 1] == "150x220")
+        XCTAssertEqual(custom[custom.firstIndex(of: "-p")! + 1], "150x220")
     }
 
-    @Test("Custom page below 50 mm throws")
-    func customPageTooSmall() {
-        #expect(throws: PrinttargArgError.self) {
-            try PrinttargArgs.build(config: config(pageSize: .custom, customW: 49.9))
+    func testCustomPageTooSmall() {
+        XCTAssertThrowsError(try PrinttargArgs.build(config: config(pageSize: .custom, customW: 49.9))) { error in
+            XCTAssertTrue(error is PrinttargArgError)
         }
-        #expect(throws: PrinttargArgError.self) {
-            try PrinttargArgs.build(config: config(pageSize: .custom, customH: 10))
+        XCTAssertThrowsError(try PrinttargArgs.build(config: config(pageSize: .custom, customH: 10))) { error in
+            XCTAssertTrue(error is PrinttargArgError)
         }
     }
 
-    @Test("Calibration: -K applies, -I embeds")
-    func calibrationFlags() throws {
+    func testCalibrationFlags() throws {
         let k = try PrinttargArgs.build(config: config(calFile: "/tmp/a.cal"))
-        #expect(k[k.firstIndex(of: "-K")! + 1] == "/tmp/a.cal")
+        XCTAssertEqual(k[k.firstIndex(of: "-K")! + 1], "/tmp/a.cal")
         let i = try PrinttargArgs.build(config: config(calFile: "/tmp/a.cal", calEmbed: true))
-        #expect(i[i.firstIndex(of: "-I")! + 1] == "/tmp/a.cal")
-        #expect(!i.contains("-K"))
+        XCTAssertEqual(i[i.firstIndex(of: "-I")! + 1], "/tmp/a.cal")
+        XCTAssertFalse(i.contains("-K"))
     }
 
-    @Test("CAL_ basename never gets -K or -I")
-    func calProtection() throws {
+    func testCalProtection() throws {
         let args = try PrinttargArgs.build(
             config: config(calFile: "/tmp/a.cal", basename: "CAL_test"))
-        #expect(!args.contains("-K"))
-        #expect(!args.contains("-I"))
+        XCTAssertFalse(args.contains("-K"))
+        XCTAssertFalse(args.contains("-I"))
     }
 
-    @Test("Whitespace-only label emits no -d; whitespace-only calibration emits no -K/-I")
-    func whitespaceOptions() throws {
+    func testWhitespaceOptions() throws {
         let args = try PrinttargArgs.build(
             config: config(label: "   \n ", calFile: " \t "))
-        #expect(!args.contains("-d"))
-        #expect(!args.contains("-K"))
-        #expect(!args.contains("-I"))
+        XCTAssertFalse(args.contains("-d"))
+        XCTAssertFalse(args.contains("-K"))
+        XCTAssertFalse(args.contains("-I"))
     }
 
-    @Test("Label and calibration values are trimmed before emission")
-    func trimmedOptions() throws {
+    func testTrimmedOptions() throws {
         let args = try PrinttargArgs.build(
             config: config(label: "  My Label  ", calFile: "  /tmp/a.cal  "))
-        #expect(args[args.firstIndex(of: "-d")! + 1] == "My Label")
-        #expect(args[args.firstIndex(of: "-K")! + 1] == "/tmp/a.cal")
+        XCTAssertEqual(args[args.firstIndex(of: "-d")! + 1], "My Label")
+        XCTAssertEqual(args[args.firstIndex(of: "-K")! + 1], "/tmp/a.cal")
     }
 
-    @Test("Unsafe basename throws")
-    func unsafeBasename() {
-        #expect(throws: PathSecurity.Error.self) {
-            try PrinttargArgs.build(config: config(basename: "../x"))
+    func testUnsafeBasename() {
+        XCTAssertThrowsError(try PrinttargArgs.build(config: config(basename: "../x"))) { error in
+            XCTAssertTrue(error is PathSecurity.Error)
         }
     }
 }
 
-@Suite("PrinttargLabel")
-struct PrinttargLabelTests {
+final class PrinttargLabelTests: XCTestCase {
 
     private var fixedDate: Date {
         var comps = DateComponents()
@@ -166,37 +151,33 @@ struct PrinttargLabelTests {
         return Calendar(identifier: .gregorian).date(from: comps)!
     }
 
-    @Test("Automatic label: ICCery - basename - P - I - DP - AP - DD/MM/YYYY HH:MM")
-    func automatic() {
+    func testAutomatic() {
         let label = PrinttargLabel.automatic(
             basename: "tgt",
             metadata: TargetLabelMetadata(
                 printer: "Epson", inkSet: "CMYK",
                 driverPaper: "Photo", actualPaper: "Matte"),
             date: fixedDate, timeZone: .current)
-        #expect(label.hasPrefix("ICCery - tgt - Epson - CMYK - Photo - Matte - "))
-        #expect(label.hasSuffix("03/02/2026") || label.contains("/02/2026"))
+        XCTAssertTrue(label.hasPrefix("ICCery - tgt - Epson - CMYK - Photo - Matte - "))
+        XCTAssertTrue(label.hasSuffix("03/02/2026") || label.contains("/02/2026"))
     }
 
-    @Test("Missing metadata becomes Unspecified")
-    func unspecified() {
+    func testUnspecified() {
         let label = PrinttargLabel.automatic(
             basename: "tgt", metadata: TargetLabelMetadata(),
             date: fixedDate, timeZone: .current)
-        #expect(label.contains(" - Unspecified - Unspecified - Unspecified - Unspecified - "))
+        XCTAssertTrue(label.contains(" - Unspecified - Unspecified - Unspecified - Unspecified - "))
     }
 
-    @Test("Manual label wins over automatic")
-    func manualWins() {
+    func testManualWins() {
         let resolved = PrinttargLabel.resolved(
             customLabel: "  My Label  ", basename: "tgt",
             metadata: TargetLabelMetadata(), date: fixedDate)
-        #expect(resolved == "My Label")
+        XCTAssertEqual(resolved, "My Label")
     }
 }
 
-@Suite("PrinttargManifest")
-struct PrinttargManifestTests {
+final class PrinttargManifestTests: XCTestCase {
 
     private let prettySingle = """
         Some log line
@@ -225,59 +206,52 @@ struct PrinttargManifestTests {
         }
         """
 
-    @Test("Decodes a single-page pretty manifest amid log noise")
-    func singlePage() throws {
+    func testSinglePage() throws {
         let m = try PrinttargManifestExtractor.manifest(from: prettySingle)
-        #expect(m.event == "manifest")
-        #expect(m.pages.count == 1)
-        #expect(m.pages[0].filename == "target.tif")
-        #expect(m.pages[0].patches == 800)
+        XCTAssertEqual(m.event, "manifest")
+        XCTAssertEqual(m.pages.count, 1)
+        XCTAssertEqual(m.pages[0].filename, "target.tif")
+        XCTAssertEqual(m.pages[0].patches, 800)
     }
 
-    @Test("Multi-page manifest preserves order")
-    func multiPage() throws {
+    func testMultiPage() throws {
         let m = try PrinttargManifestExtractor.manifest(from: prettyMulti)
-        #expect(m.pages.map(\.filename) == ["p1.tif", "p2.tif"])
+        XCTAssertEqual(m.pages.map(\.filename), ["p1.tif", "p2.tif"])
     }
 
-    @Test("No JSON document → noJSONDocument")
-    func noJSON() {
-        #expect(throws: ManifestError.self) {
-            try PrinttargManifestExtractor.manifest(from: "plain text\nno json")
+    func testNoJSON() {
+        XCTAssertThrowsError(try PrinttargManifestExtractor.manifest(from: "plain text\nno json")) { error in
+            XCTAssertTrue(error is ManifestError)
         }
     }
 
-    @Test("Wrong event → wrongEvent")
-    func wrongEvent() {
+    func testWrongEvent() {
         let stdout = "{\n  \"event\": \"row\",\n  \"row\": 1\n}\n"
-        #expect(throws: ManifestError.self) {
-            try PrinttargManifestExtractor.manifest(from: stdout)
+        XCTAssertThrowsError(try PrinttargManifestExtractor.manifest(from: stdout)) { error in
+            XCTAssertTrue(error is ManifestError)
         }
     }
 
-    @Test("ROW_COLORS_JSON line is never treated as the manifest")
-    func rowColorsNotManifest() {
+    func testRowColorsNotManifest() {
         let stdout = "ROW_COLORS_JSON: {\"a\":1}\n{\"event\":\"manifest\",\"pages\":[]}"
         // Extraction only starts at a '{' that begins a trimmed line,
         // so the ROW_COLORS_JSON line is skipped entirely.
         let m = try? PrinttargManifestExtractor.manifest(from: stdout)
-        #expect(m != nil)
-        #expect(m?.event == "manifest")
+        XCTAssertNotNil(m)
+        XCTAssertEqual(m?.event, "manifest")
     }
 
-    @Test("Braces inside a quoted filename do not corrupt the scan")
-    func bracesInFilename() throws {
+    func testBracesInFilename() throws {
         let stdout = "log\n{\n\"event\": \"manifest\",\n\"pages\": [{\"filename\": \"a}b.tif\", \"patches\": 1, \"width_mm\": 50, \"height_mm\": 50}]\n}\n"
         let m = try PrinttargManifestExtractor.manifest(from: stdout)
-        #expect(m.pages[0].filename == "a}b.tif")
+        XCTAssertEqual(m.pages[0].filename, "a}b.tif")
     }
 
-    @Test("Unsafe / non-TIFF filenames rejected")
-    func unsafeFilenames() {
+    func testUnsafeFilenames() {
         for bad in ["../x.tif", "/abs/x.tif", "dir/x.tif", "x.txt", ""] {
             let stdout = "{\n\"event\":\"manifest\",\"pages\":[{\"filename\":\"\(bad)\",\"patches\":1,\"width_mm\":50,\"height_mm\":50}]\n}"
-            #expect(throws: ManifestError.self) {
-                try PrinttargManifestExtractor.manifest(from: stdout)
+            XCTAssertThrowsError(try PrinttargManifestExtractor.manifest(from: stdout)) { error in
+                XCTAssertTrue(error is ManifestError)
             }
         }
     }
diff --git a/Tests/ICCeryCoreTests/ProcessManagerTests.swift b/Tests/ICCeryCoreTests/ProcessManagerTests.swift
index 716bf92..d3a3f3a 100644
--- a/Tests/ICCeryCoreTests/ProcessManagerTests.swift
+++ b/Tests/ICCeryCoreTests/ProcessManagerTests.swift
@@ -1,4 +1,5 @@
 import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 
@@ -408,65 +409,62 @@ struct ProcessManagerTests {
     }
 }
 
-@Suite("ProcessLineDecoder")
-struct ProcessLineDecoderTests {
-    @Test func splitsAcrossChunkBoundaries() {
+final class ProcessLineDecoderTests: XCTestCase {
+    func testSplitsAcrossChunkBoundaries() {
         var d = ProcessLineDecoder()
-        #expect(d.feed(Data("he".utf8)) == [])
-        #expect(d.feed(Data("llo\nwor".utf8)) == ["hello"])
-        #expect(d.feed(Data("ld\n".utf8)) == ["world"])
-        #expect(d.finish() == nil)
+        XCTAssertEqual(d.feed(Data("he".utf8)), [])
+        XCTAssertEqual(d.feed(Data("llo\nwor".utf8)), ["hello"])
+        XCTAssertEqual(d.feed(Data("ld\n".utf8)), ["world"])
+        XCTAssertNil(d.finish())
     }
 
-    @Test func crlfIsStripped() {
+    func testCrlfIsStripped() {
         var d = ProcessLineDecoder()
-        #expect(d.feed(Data("a\r\nb\r\n".utf8)) == ["a", "b"])
+        XCTAssertEqual(d.feed(Data("a\r\nb\r\n".utf8)), ["a", "b"])
     }
 
-    @Test func finishReturnsRemainder() {
+    func testFinishReturnsRemainder() {
         var d = ProcessLineDecoder()
         _ = d.feed(Data("x".utf8))
-        #expect(d.finish() == "x")
-        #expect(d.finish() == nil)
+        XCTAssertEqual(d.finish(), "x")
+        XCTAssertNil(d.finish())
     }
 }
 
-@Suite("JSONAccumulator")
-struct JSONAccumulatorTests {
-    @Test func multilinePrettyJSON() {
+final class JSONAccumulatorTests: XCTestCase {
+    func testMultilinePrettyJSON() {
         var acc = JSONAccumulator()
-        #expect(acc.feed(line: "{") == nil)
-        #expect(acc.feed(line: "  \"k\": 1") == nil)
+        XCTAssertNil(acc.feed(line: "{"))
+        XCTAssertNil(acc.feed(line: "  \"k\": 1"))
         let done = acc.feed(line: "}")
-        #expect(done != nil)
+        XCTAssertNotNil(done)
         let obj = try? JSONSerialization.jsonObject(with: done!) as? [String: Int]
-        #expect(obj?["k"] == 1)
+        XCTAssertEqual(obj?["k"], 1)
     }
 
-    @Test func nonJSONLinesIgnored() {
+    func testNonJSONLinesIgnored() {
         var acc = JSONAccumulator()
-        #expect(acc.feed(line: "Reading instrument...") == nil)
-        #expect(acc.feed(line: "still text") == nil)
-        #expect(acc.completeData == nil)
+        XCTAssertNil(acc.feed(line: "Reading instrument..."))
+        XCTAssertNil(acc.feed(line: "still text"))
+        XCTAssertNil(acc.completeData)
     }
 
-    @Test func decodeTyped() {
+    func testDecodeTyped() {
         struct Doc: Decodable { let n: Int }
         var acc = JSONAccumulator()
         // Split so the doc completes on the second feed.
-        #expect(acc.feed(line: "{\"n\":") == nil)
+        XCTAssertNil(acc.feed(line: "{\"n\":"))
         let data = acc.feed(line: "7}")
-        #expect(data != nil)
+        XCTAssertNotNil(data)
         let doc = data.flatMap { try? JSONDecoder().decode(Doc.self, from: $0) }
-        #expect(doc?.n == 7)
-        #expect(acc.isEmpty)
+        XCTAssertEqual(doc?.n, 7)
+        XCTAssertTrue(acc.isEmpty)
     }
 }
 
-@Suite("LogSanitizer")
-struct LogSanitizerTests {
-    @Test func homeIsRewritten() {
+final class LogSanitizerTests: XCTestCase {
+    func testHomeIsRewritten() {
         let path = "\(NSHomeDirectory())/Documents/foo.ti1"
-        #expect(LogSanitizer.sanitize(path) == "~/Documents/foo.ti1")
+        XCTAssertEqual(LogSanitizer.sanitize(path), "~/Documents/foo.ti1")
     }
 }
diff --git a/Tests/ICCeryCoreTests/ProfcheckArgsTests.swift b/Tests/ICCeryCoreTests/ProfcheckArgsTests.swift
index 4ac887d..09b461f 100644
--- a/Tests/ICCeryCoreTests/ProfcheckArgsTests.swift
+++ b/Tests/ICCeryCoreTests/ProfcheckArgsTests.swift
@@ -1,17 +1,15 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("ProfcheckArgs")
-struct ProfcheckArgsTests {
+final class ProfcheckArgsTests: XCTestCase {
 
-    @Test("Hard-coded argv")
-    func argv() throws {
+    func testArgv() throws {
         let config = ProfcheckConfig(
             ti3URL: URL(fileURLWithPath: "/tmp/target.ti3"),
             iccURL: URL(fileURLWithPath: "/tmp/target.icc")
         )
         let args = try ProfcheckArgs.build(config: config)
-        #expect(args == ["-v", "-k", "-s", "-u", "/tmp/target.ti3", "/tmp/target.icc"])
+        XCTAssertEqual(args, ["-v", "-k", "-s", "-u", "/tmp/target.ti3", "/tmp/target.icc"])
     }
 }
diff --git a/Tests/ICCeryCoreTests/ProfcheckParserTests.swift b/Tests/ICCeryCoreTests/ProfcheckParserTests.swift
index 30ea74f..50b165d 100644
--- a/Tests/ICCeryCoreTests/ProfcheckParserTests.swift
+++ b/Tests/ICCeryCoreTests/ProfcheckParserTests.swift
@@ -1,43 +1,39 @@
 import Foundation
-import Testing
+import XCTest
 @testable import ICCeryCore
 
-@Suite("ProfcheckParser")
-struct ProfcheckParserTests {
+final class ProfcheckParserTests: XCTestCase {
 
-    @Test("Prefers JSON report with de2000 keys")
-    func jsonReport() {
+    func testJsonReport() {
         let output = """
         No of test patches = 52
         {"event": "report", "peak_de2000": 2.41, "avg_de2000": 0.85, "rms": 1.02}
         Profile check complete, errors(CIEDE2000): max. = 9.99, avg. = 9.99, RMS = 9.99
         """
         let report = ProfcheckParser.parse(output)
-        #expect(report.isValid == true)
-        #expect(report.patchCount == 52)
-        #expect(report.avgDE == 0.85)
-        #expect(report.maxDE == 2.41)
-        #expect(report.rmsDE == 1.02)
-        #expect(report.status == .excellent)
+        XCTAssertEqual(report.isValid, true)
+        XCTAssertEqual(report.patchCount, 52)
+        XCTAssertEqual(report.avgDE, 0.85)
+        XCTAssertEqual(report.maxDE, 2.41)
+        XCTAssertEqual(report.rmsDE, 1.02)
+        XCTAssertEqual(report.status, .excellent)
     }
 
-    @Test("Falls back to legacy text")
-    func legacyText() {
+    func testLegacyText() {
         let output = """
         No of test patches = 120
         Profile check complete, errors(CIEDE2000): max. = 3.50, avg. = 1.80, RMS = 0.95
         """
         let report = ProfcheckParser.parse(output)
-        #expect(report.isValid == true)
-        #expect(report.patchCount == 120)
-        #expect(report.avgDE == 1.80)
-        #expect(report.maxDE == 3.50)
-        #expect(report.rmsDE == 0.95)
-        #expect(report.status == .good)
+        XCTAssertEqual(report.isValid, true)
+        XCTAssertEqual(report.patchCount, 120)
+        XCTAssertEqual(report.avgDE, 1.80)
+        XCTAssertEqual(report.maxDE, 3.50)
+        XCTAssertEqual(report.rmsDE, 0.95)
+        XCTAssertEqual(report.status, .good)
     }
 
-    @Test("Broad regex fallback")
-    func regexFallback() {
+    func testRegexFallback() {
         let output = """
         No of test patches = 10
         avg = 4.25
@@ -45,27 +41,25 @@ struct ProfcheckParserTests {
         rms = 2.30
         """
         let report = ProfcheckParser.parse(output)
-        #expect(report.isValid == true)
-        #expect(report.avgDE == 4.25)
-        #expect(report.maxDE == 6.10)
-        #expect(report.rmsDE == 2.30)
-        #expect(report.status == .poor)
+        XCTAssertEqual(report.isValid, true)
+        XCTAssertEqual(report.avgDE, 4.25)
+        XCTAssertEqual(report.maxDE, 6.10)
+        XCTAssertEqual(report.rmsDE, 2.30)
+        XCTAssertEqual(report.status, .poor)
     }
 
-    @Test("Unparseable output warns, not zeros")
-    func unparseable() {
+    func testUnparseable() {
         let output = "some random text without metrics"
         let report = ProfcheckParser.parse(output)
-        #expect(report.isValid == false)
-        #expect(report.warning != nil)
-        #expect(report.avgDE == nil)
+        XCTAssertEqual(report.isValid, false)
+        XCTAssertNotNil(report.warning)
+        XCTAssertNil(report.avgDE)
     }
 
-    @Test("Status bands")
-    func statusBands() {
-        #expect(VerificationStatus.from(avgDE: 0.5) == .excellent)
-        #expect(VerificationStatus.from(avgDE: 1.5) == .good)
-        #expect(VerificationStatus.from(avgDE: 2.5) == .acceptable)
-        #expect(VerificationStatus.from(avgDE: 4.0) == .poor)
+    func testStatusBands() {
+        XCTAssertEqual(VerificationStatus.from(avgDE: 0.5), .excellent)
+        XCTAssertEqual(VerificationStatus.from(avgDE: 1.5), .good)
+        XCTAssertEqual(VerificationStatus.from(avgDE: 2.5), .acceptable)
+        XCTAssertEqual(VerificationStatus.from(avgDE: 4.0), .poor)
     }
 }
diff --git a/Tests/ICCeryCoreTests/TargenTests.swift b/Tests/ICCeryCoreTests/TargenTests.swift
index 821efce..c11a0a1 100644
--- a/Tests/ICCeryCoreTests/TargenTests.swift
+++ b/Tests/ICCeryCoreTests/TargenTests.swift
@@ -1,12 +1,11 @@
 import Testing
+import XCTest
 import Foundation
 @testable import ICCeryCore
 
-@Suite("TargenArgs")
-struct TargenArgsTests {
+final class TargenArgsTests: XCTestCase {
 
-    @Test("RGB baseline: -v -d 2 -f 800 -e 4 -B 4")
-    func rgbBaseline() throws {
+    func testRgbBaseline() throws {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 800,
@@ -15,12 +14,11 @@ struct TargenArgsTests {
             basename: "test_rgb"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(args == ["-v", "-d", "2", "-f", "800", "-e", "4", "-B", "4", "test_rgb"])
-        #expect(!args.contains("-u"))
+        XCTAssertEqual(args, ["-v", "-d", "2", "-f", "800", "-e", "4", "-B", "4", "test_rgb"])
+        XCTAssertFalse(args.contains("-u"))
     }
 
-    @Test("CMYK baseline: -v -d 4 -f 1500 -e 4 -B 0")
-    func cmykBaseline() throws {
+    func testCmykBaseline() throws {
         let config = TargenConfig(
             colourSpace: .cmyk,
             patchCount: 1500,
@@ -29,11 +27,10 @@ struct TargenArgsTests {
             basename: "test_cmyk"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(args == ["-v", "-d", "4", "-f", "1500", "-e", "4", "-B", "0", "test_cmyk"])
+        XCTAssertEqual(args, ["-v", "-d", "4", "-f", "1500", "-e", "4", "-B", "0", "test_cmyk"])
     }
 
-    @Test("Custom patch count honours -f (#44)")
-    func customPatchCount() throws {
+    func testCustomPatchCount() throws {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 2500,
@@ -42,12 +39,11 @@ struct TargenArgsTests {
             basename: "custom_patches"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(args.contains("-f"))
-        #expect(args[args.firstIndex(of: "-f")! + 1] == "2500")
+        XCTAssertTrue(args.contains("-f"))
+        XCTAssertEqual(args[args.firstIndex(of: "-f")! + 1], "2500")
     }
 
-    @Test("All advanced flags in stable order")
-    func allAdvancedFlags() throws {
+    func testAllAdvancedFlags() throws {
         let config = TargenConfig(
             colourSpace: .cmyk,
             patchCount: 1200,
@@ -85,11 +81,10 @@ struct TargenArgsTests {
             "-p", "2.00",
             "advanced_cmyk"
         ]
-        #expect(args == expected)
+        XCTAssertEqual(args, expected)
     }
 
-    @Test("RGB ignores total ink limit")
-    func rgbIgnoresInkLimit() throws {
+    func testRgbIgnoresInkLimit() throws {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 800,
@@ -99,11 +94,10 @@ struct TargenArgsTests {
             basename: "rgb_no_ink"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(!args.contains("-l"))
+        XCTAssertFalse(args.contains("-l"))
     }
 
-    @Test("Neutral concentration omitted when approximately 0.50")
-    func neutralConcentrationOmittedWhenDefault() throws {
+    func testNeutralConcentrationOmittedWhenDefault() throws {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 800,
@@ -113,11 +107,10 @@ struct TargenArgsTests {
             basename: "n_default"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(!args.contains("-N"))
+        XCTAssertFalse(args.contains("-N"))
     }
 
-    @Test("Adaptation emitted even at 0.10 (no default-skip)")
-    func adaptationEmittedAtPointOne() throws {
+    func testAdaptationEmittedAtPointOne() throws {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 800,
@@ -127,12 +120,11 @@ struct TargenArgsTests {
             basename: "a_flag"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(args.contains("-A"))
-        #expect(args[args.firstIndex(of: "-A")! + 1] == "0.10")
+        XCTAssertTrue(args.contains("-A"))
+        XCTAssertEqual(args[args.firstIndex(of: "-A")! + 1], "0.10")
     }
 
-    @Test("OFPS full spread algorithm emits no flag")
-    func ofpsEmitsNoFlag() throws {
+    func testOfpsEmitsNoFlag() throws {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 800,
@@ -142,12 +134,11 @@ struct TargenArgsTests {
             basename: "ofps_test"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(!args.contains("ofps"))
-        #expect(!args.contains("-t"))
+        XCTAssertFalse(args.contains("ofps"))
+        XCTAssertFalse(args.contains("-t"))
     }
 
-    @Test("Dark emphasis and device power omitted when 1.0")
-    func darkEmphasisAndPowerOmittedWhenOne() throws {
+    func testDarkEmphasisAndPowerOmittedWhenOne() throws {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 800,
@@ -158,12 +149,11 @@ struct TargenArgsTests {
             basename: "defaults_omitted"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(!args.contains("-V"))
-        #expect(!args.contains("-p"))
+        XCTAssertFalse(args.contains("-V"))
+        XCTAssertFalse(args.contains("-p"))
     }
 
-    @Test("Whitespace-only preconditioning profile emits no -c")
-    func whitespacePreconditioner() throws {
+    func testWhitespacePreconditioner() throws {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 800,
@@ -173,11 +163,10 @@ struct TargenArgsTests {
             basename: "ws_pre"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(!args.contains("-c"))
+        XCTAssertFalse(args.contains("-c"))
     }
 
-    @Test("Preconditioning profile is trimmed before emission")
-    func preconditionerTrimmed() throws {
+    func testPreconditionerTrimmed() throws {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 800,
@@ -187,11 +176,10 @@ struct TargenArgsTests {
             basename: "trim_pre"
         )
         let args = try TargenArgs.build(config: config)
-        #expect(args[args.firstIndex(of: "-c")! + 1] == "/path/to/profile.icc")
+        XCTAssertEqual(args[args.firstIndex(of: "-c")! + 1], "/path/to/profile.icc")
     }
 
-    @Test("Invalid basename throws")
-    func invalidBasenameThrows() {
+    func testInvalidBasenameThrows() {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 800,
@@ -199,13 +187,12 @@ struct TargenArgsTests {
             blackPatches: 4,
             basename: "../bad_name"
         )
-        #expect(throws: PathSecurity.Error.self) {
-            try TargenArgs.build(config: config)
+        XCTAssertThrowsError(try TargenArgs.build(config: config)) { error in
+            XCTAssertTrue(error is PathSecurity.Error)
         }
     }
 
-    @Test("Invalid patch count throws")
-    func invalidPatchCountThrows() {
+    func testInvalidPatchCountThrows() {
         let config = TargenConfig(
             colourSpace: .rgb,
             patchCount: 0,
@@ -213,13 +200,12 @@ struct TargenArgsTests {
             blackPatches: 4,
             basename: "bad_count"
         )
-        #expect(throws: TargenArgError.self) {
-            try TargenArgs.build(config: config)
+        XCTAssertThrowsError(try TargenArgs.build(config: config)) { error in
+            XCTAssertTrue(error is TargenArgError)
         }
     }
 
-    @Test("Invalid ink limit throws for CMYK")
-    func invalidInkLimitThrows() {
+    func testInvalidInkLimitThrows() {
         let config = TargenConfig(
             colourSpace: .cmyk,
             patchCount: 800,
@@ -228,8 +214,8 @@ struct TargenArgsTests {
             totalInkLimit: 450,
             basename: "bad_ink"
         )
-        #expect(throws: TargenArgError.self) {
-            try TargenArgs.build(config: config)
+        XCTAssertThrowsError(try TargenArgs.build(config: config)) { error in
+            XCTAssertTrue(error is TargenArgError)
         }
     }
 }
diff --git a/Tests/ICCeryCoreTests/TestAppEnvironment.swift b/Tests/ICCeryCoreTests/TestAppEnvironment.swift
index ac27fe4..1a7f9d0 100644
--- a/Tests/ICCeryCoreTests/TestAppEnvironment.swift
+++ b/Tests/ICCeryCoreTests/TestAppEnvironment.swift
@@ -1,4 +1,3 @@
-import Testing
 import Foundation
 @testable import ICCeryCore
 @testable import ICCery
diff --git a/Tests/ICCeryCoreTests/XCTestCase+AsyncThrows.swift b/Tests/ICCeryCoreTests/XCTestCase+AsyncThrows.swift
new file mode 100644
index 0000000..c26ea15
--- /dev/null
+++ b/Tests/ICCeryCoreTests/XCTestCase+AsyncThrows.swift
@@ -0,0 +1,21 @@
+import XCTest
+
+extension XCTestCase {
+    func assertAsyncThrows<T, E: Error>(
+        expectedType: E.Type,
+        _ expression: () async throws -> T,
+        _ message: @autoclosure () -> String = "",
+        file: StaticString = #filePath,
+        line: UInt = #line,
+        errorHandler: ((E) -> Void)? = nil
+    ) async {
+        do {
+            _ = try await expression()
+            XCTFail("Expected \(expectedType) to be thrown but expression succeeded. \(message())", file: file, line: line)
+        } catch let error as E {
+            errorHandler?(error)
+        } catch {
+            XCTFail("Expected \(expectedType) but caught \(type(of: error)): \(error). \(message())", file: file, line: line)
+        }
+    }
+}