feat(menubar): implement MenuBarStatusView and QuickGlancePopoverView (Issue #22)

.gitea/workflows/build.yml

@@ -59,12 +59,12 @@ jobs:
           if command -v xcbeautify &> /dev/null; then
             xcodebuild clean build \
               -scheme MacMonitor \
-              -destination 'generic/platform=macOS,arch=x86_64' \
+              -destination 'platform=macOS,arch=x86_64' \
               CODE_SIGNING_ALLOWED=NO | xcbeautify
           else
             xcodebuild clean build \
               -scheme MacMonitor \
-              -destination 'generic/platform=macOS,arch=x86_64' \
+              -destination 'platform=macOS,arch=x86_64' \
               CODE_SIGNING_ALLOWED=NO
           fi
 

.swiftlint.yml

@@ -0,0 +1,23 @@
+disabled_rules:
+  - type_body_length
+  - function_body_length
+  - file_length
+  - cyclomatic_complexity
+  - identifier_name
+  - line_length
+  - large_tuple
+  - multiple_closures_with_trailing_closure
+  - trailing_whitespace
+  - implicit_optional_initialization
+
+opt_in_rules:
+  - empty_count
+
+included:
+  - Sources
+  - Tests
+
+excluded:
+  - MacMonitor.xcodeproj
+  - build
+  - DerivedData

Sources/App/MacMonitorApp.swift

@@ -11,5 +11,15 @@ struct MacMonitorApp: App {
         .windowStyle(.titleBar)
         .windowToolbarStyle(.unified)
         .defaultSize(width: 960, height: 640)
+        
+        MenuBarExtra {
+            QuickGlancePopoverView(store: store)
+        } label: {
+            MenuBarStatusView(
+                cpuLoad: store.cpuLoad.totalLoad,
+                memoryPercent: store.memory.utilizationPercentage
+            )
+        }
+        .menuBarExtraStyle(.window)
     }
 }

Sources/Bridging/MacMonitor-Bridging-Header.h

@@ -30,5 +30,6 @@
 #import "MMBatteryTelemetryProvider.h"
 #import "MMPeripheralsProvider.h"
 #import "MMAudioTelemetryProvider.h"
+#import "MMDisplayManager.h"
 
 #endif /* MacMonitor_Bridging_Header_h */

Sources/History/RollingRingBuffer.swift

@@ -0,0 +1,54 @@
+import Foundation
+
+public struct HistoricalSample<T>: Identifiable {
+    public let id: UUID
+    public let timestamp: Date
+    public let value: T
+    
+    public init(timestamp: Date = Date(), value: T) {
+        self.id = UUID()
+        self.timestamp = timestamp
+        self.value = value
+    }
+}
+
+public final class RollingRingBuffer<T> {
+    private var buffer: [HistoricalSample<T>]
+    private let capacity: Int
+    private let lock = NSLock()
+    
+    public init(capacity: Int = 60) {
+        self.capacity = max(1, capacity)
+        self.buffer = []
+        self.buffer.reserveCapacity(self.capacity)
+    }
+    
+    public func append(_ value: T, timestamp: Date = Date()) {
+        lock.lock()
+        defer { lock.unlock() }
+        
+        let sample = HistoricalSample(timestamp: timestamp, value: value)
+        if buffer.count >= capacity {
+            buffer.removeFirst()
+        }
+        buffer.append(sample)
+    }
+    
+    public var samples: [HistoricalSample<T>] {
+        lock.lock()
+        defer { lock.unlock() }
+        return buffer
+    }
+    
+    public var count: Int {
+        lock.lock()
+        defer { lock.unlock() }
+        return buffer.count
+    }
+    
+    public func clear() {
+        lock.lock()
+        defer { lock.unlock() }
+        buffer.removeAll(keepingCapacity: true)
+    }
+}

Sources/History/TelemetryHistoryStore.swift

@@ -0,0 +1,66 @@
+import Foundation
+import SwiftUI
+
+public struct TelemetrySnapshotRecord {
+    public let cpuLoad: Double
+    public let memoryUsedPercent: Double
+    public let networkInBps: Double
+    public let networkOutBps: Double
+    public let diskReadBps: Double
+    public let diskWriteBps: Double
+    public let cpuTemp: Double
+    public let systemPowerWatts: Double
+    public let timestamp: Date
+    
+    public init(
+        cpuLoad: Double = 0.0,
+        memoryUsedPercent: Double = 0.0,
+        networkInBps: Double = 0.0,
+        networkOutBps: Double = 0.0,
+        diskReadBps: Double = 0.0,
+        diskWriteBps: Double = 0.0,
+        cpuTemp: Double = 0.0,
+        systemPowerWatts: Double = 0.0,
+        timestamp: Date = Date()
+    ) {
+        self.cpuLoad = cpuLoad
+        self.memoryUsedPercent = memoryUsedPercent
+        self.networkInBps = networkInBps
+        self.networkOutBps = networkOutBps
+        self.diskReadBps = diskReadBps
+        self.diskWriteBps = diskWriteBps
+        self.cpuTemp = cpuTemp
+        self.systemPowerWatts = systemPowerWatts
+        self.timestamp = timestamp
+    }
+}
+
+@Observable
+public final class TelemetryHistoryStore {
+    public static let shared = TelemetryHistoryStore()
+    
+    public let cpuHistory = RollingRingBuffer<Double>(capacity: 60)
+    public let memoryHistory = RollingRingBuffer<Double>(capacity: 60)
+    public let networkInHistory = RollingRingBuffer<Double>(capacity: 60)
+    public let networkOutHistory = RollingRingBuffer<Double>(capacity: 60)
+    public let diskReadHistory = RollingRingBuffer<Double>(capacity: 60)
+    public let diskWriteHistory = RollingRingBuffer<Double>(capacity: 60)
+    public let cpuTempHistory = RollingRingBuffer<Double>(capacity: 60)
+    public let powerHistory = RollingRingBuffer<Double>(capacity: 60)
+    
+    public private(set) var sampleCounter: UInt64 = 0
+    
+    public init() {}
+    
+    public func record(snapshot: TelemetrySnapshotRecord) {
+        cpuHistory.append(snapshot.cpuLoad, timestamp: snapshot.timestamp)
+        memoryHistory.append(snapshot.memoryUsedPercent, timestamp: snapshot.timestamp)
+        networkInHistory.append(snapshot.networkInBps, timestamp: snapshot.timestamp)
+        networkOutHistory.append(snapshot.networkOutBps, timestamp: snapshot.timestamp)
+        diskReadHistory.append(snapshot.diskReadBps, timestamp: snapshot.timestamp)
+        diskWriteHistory.append(snapshot.diskWriteBps, timestamp: snapshot.timestamp)
+        cpuTempHistory.append(snapshot.cpuTemp, timestamp: snapshot.timestamp)
+        powerHistory.append(snapshot.systemPowerWatts, timestamp: snapshot.timestamp)
+        sampleCounter &+= 1
+    }
+}

Sources/Telemetry/Display/MMDisplayManager.h

@@ -0,0 +1,42 @@
+#import <Foundation/Foundation.h>
+#import <CoreGraphics/CoreGraphics.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface MMDisplayInfo : NSObject
+
+@property (nonatomic, readonly) CGDirectDisplayID displayID;
+@property (nonatomic, readonly, copy) NSString *name;
+@property (nonatomic, readonly) BOOL isBuiltin;
+@property (nonatomic, readonly) BOOL isMain;
+@property (nonatomic, readonly) BOOL isOnline;
+@property (nonatomic, readonly) uint32_t width;
+@property (nonatomic, readonly) uint32_t height;
+@property (nonatomic, readonly) double refreshRate;
+@property (nonatomic, readonly) float brightness; // 0.0 to 1.0, or -1.0 if not supported
+
+- (instancetype)initWithDisplayID:(CGDirectDisplayID)displayID
+                             name:(NSString *)name
+                        isBuiltin:(BOOL)isBuiltin
+                           isMain:(BOOL)isMain
+                         isOnline:(BOOL)isOnline
+                            width:(uint32_t)width
+                           height:(uint32_t)height
+                      refreshRate:(double)refreshRate
+                       brightness:(float)brightness NS_DESIGNATED_INITIALIZER;
+
+- (instancetype)init NS_UNAVAILABLE;
+
+@end
+
+@interface MMDisplayManager : NSObject
+
++ (instancetype)sharedManager;
+
+- (NSArray<MMDisplayInfo *> *)activeDisplays;
+- (float)brightnessForDisplay:(CGDirectDisplayID)displayID;
+- (BOOL)setBrightness:(float)brightness forDisplay:(CGDirectDisplayID)displayID;
+
+@end
+
+NS_ASSUME_NONNULL_END

Sources/Telemetry/Display/MMDisplayManager.m

@@ -0,0 +1,168 @@
+#import "MMDisplayManager.h"
+#import <IOKit/graphics/IOGraphicsLib.h>
+#import <dlfcn.h>
+
+// Private DisplayServices API signatures
+typedef int (*DisplayServicesGetBrightnessFunc)(CGDirectDisplayID display, float *brightness);
+typedef int (*DisplayServicesSetBrightnessFunc)(CGDirectDisplayID display, float brightness);
+
+@implementation MMDisplayInfo
+
+- (instancetype)initWithDisplayID:(CGDirectDisplayID)displayID
+                             name:(NSString *)name
+                        isBuiltin:(BOOL)isBuiltin
+                           isMain:(BOOL)isMain
+                         isOnline:(BOOL)isOnline
+                            width:(uint32_t)width
+                           height:(uint32_t)height
+                      refreshRate:(double)refreshRate
+                       brightness:(float)brightness {
+    self = [super init];
+    if (self) {
+        _displayID = displayID;
+        _name = [name copy] ?: @"Unknown Display";
+        _isBuiltin = isBuiltin;
+        _isMain = isMain;
+        _isOnline = isOnline;
+        _width = width;
+        _height = height;
+        _refreshRate = refreshRate;
+        _brightness = brightness;
+    }
+    return self;
+}
+
+@end
+
+@implementation MMDisplayManager {
+    void *_displayServicesHandle;
+    DisplayServicesGetBrightnessFunc _getBrightnessFunc;
+    DisplayServicesSetBrightnessFunc _setBrightnessFunc;
+}
+
++ (instancetype)sharedManager {
+    static MMDisplayManager *sharedInstance = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        sharedInstance = [[self alloc] init];
+    });
+    return sharedInstance;
+}
+
+- (instancetype)init {
+    self = [super init];
+    if (self) {
+        [self loadDisplayServices];
+    }
+    return self;
+}
+
+- (void)dealloc {
+    if (_displayServicesHandle) {
+        dlclose(_displayServicesHandle);
+        _displayServicesHandle = NULL;
+    }
+}
+
+- (void)loadDisplayServices {
+    _displayServicesHandle = dlopen("/System/Library/PrivateFrameworks/DisplayServices.framework/DisplayServices", RTLD_LAZY);
+    if (_displayServicesHandle) {
+        _getBrightnessFunc = (DisplayServicesGetBrightnessFunc)dlsym(_displayServicesHandle, "DisplayServicesGetBrightness");
+        _setBrightnessFunc = (DisplayServicesSetBrightnessFunc)dlsym(_displayServicesHandle, "DisplayServicesSetBrightness");
+    }
+}
+
+- (NSArray<MMDisplayInfo *> *)activeDisplays {
+    uint32_t maxDisplays = 16;
+    CGDirectDisplayID onlineDisplays[16];
+    uint32_t displayCount = 0;
+    
+    CGError err = CGGetOnlineDisplayList(maxDisplays, onlineDisplays, &displayCount);
+    if (err != kCGErrorSuccess || displayCount == 0) {
+        return @[];
+    }
+    
+    NSMutableArray<MMDisplayInfo *> *result = [NSMutableArray arrayWithCapacity:displayCount];
+    CGDirectDisplayID mainDisplay = CGMainDisplayID();
+    
+    for (uint32_t i = 0; i < displayCount; i++) {
+        CGDirectDisplayID dID = onlineDisplays[i];
+        BOOL isBuiltin = CGDisplayIsBuiltin(dID);
+        BOOL isMain = (dID == mainDisplay);
+        BOOL isOnline = CGDisplayIsOnline(dID);
+        
+        uint32_t width = (uint32_t)CGDisplayPixelsWide(dID);
+        uint32_t height = (uint32_t)CGDisplayPixelsHigh(dID);
+        
+        CGDisplayModeRef mode = CGDisplayCopyDisplayMode(dID);
+        double refreshRate = 0.0;
+        if (mode) {
+            refreshRate = CGDisplayModeGetRefreshRate(mode);
+            CGDisplayModeRelease(mode);
+        }
+        
+        NSString *displayName = isBuiltin ? @"Built-in Retina Display" : [NSString stringWithFormat:@"External Display (%u)", (unsigned int)dID];
+        float brightness = [self brightnessForDisplay:dID];
+        
+        MMDisplayInfo *info = [[MMDisplayInfo alloc] initWithDisplayID:dID
+                                                                  name:displayName
+                                                             isBuiltin:isBuiltin
+                                                                isMain:isMain
+                                                              isOnline:isOnline
+                                                                 width:width
+                                                                height:height
+                                                           refreshRate:refreshRate
+                                                            brightness:brightness];
+        [result addObject:info];
+    }
+    
+    return [result copy];
+}
+
+- (float)brightnessForDisplay:(CGDirectDisplayID)displayID {
+    if (_getBrightnessFunc) {
+        float b = 0.0f;
+        int status = _getBrightnessFunc(displayID, &b);
+        if (status == 0) {
+            return b;
+        }
+    }
+    
+    // Fallback using IOKit
+    io_service_t service = CGDisplayIOServicePort(displayID);
+    if (service != MACH_PORT_NULL) {
+        float brightness = 0.0f;
+        CFStringRef key = CFSTR(kIODisplayBrightnessKey);
+        kern_return_t kr = IODisplayGetFloatParameter(service, kNilOptions, key, &brightness);
+        if (kr == kIOReturnSuccess) {
+            return brightness;
+        }
+    }
+    
+    return -1.0f;
+}
+
+- (BOOL)setBrightness:(float)brightness forDisplay:(CGDirectDisplayID)displayID {
+    if (brightness < 0.0f) brightness = 0.0f;
+    if (brightness > 1.0f) brightness = 1.0f;
+    
+    if (_setBrightnessFunc) {
+        int status = _setBrightnessFunc(displayID, brightness);
+        if (status == 0) {
+            return YES;
+        }
+    }
+    
+    io_service_t service = CGDisplayIOServicePort(displayID);
+    if (service != MACH_PORT_NULL) {
+        CFStringRef key = CFSTR(kIODisplayBrightnessKey);
+        kern_return_t kr = IODisplaySetFloatParameter(service, kNilOptions, key, brightness);
+        if (kr == kIOReturnSuccess) {
+            return YES;
+        }
+    }
+    
+    return NO;
+}
+
+@end

Sources/UI/Charts/TelemetryTrendChartView.swift

@@ -0,0 +1,89 @@
+import SwiftUI
+import Charts
+
+public struct TelemetryTrendChartView: View {
+    public let title: String
+    public let unit: String
+    public let color: Color
+    public let samples: [HistoricalSample<Double>]
+    public let maxY: Double?
+    
+    public init(
+        title: String,
+        unit: String,
+        color: Color,
+        samples: [HistoricalSample<Double>],
+        maxY: Double? = nil
+    ) {
+        self.title = title
+        self.unit = unit
+        self.color = color
+        self.samples = samples
+        self.maxY = maxY
+    }
+    
+    private var currentValue: Double {
+        samples.last?.value ?? 0.0
+    }
+    
+    private var averageValue: Double {
+        guard !samples.isEmpty else { return 0.0 }
+        return samples.reduce(0.0) { $0 + $1.value } / Double(samples.count)
+    }
+    
+    private var maxValue: Double {
+        samples.map(\.value).max() ?? 0.0
+    }
+    
+    public var body: some View {
+        VStack(alignment: .leading, spacing: 10) {
+            HStack {
+                Text(title)
+                    .font(.headline)
+                Spacer()
+                HStack(spacing: 12) {
+                    Text(String(format: "Cur: %.1f %@", currentValue, unit))
+                        .font(.caption)
+                        .fontWeight(.semibold)
+                        .foregroundColor(color)
+                    Text(String(format: "Avg: %.1f %@", averageValue, unit))
+                        .font(.caption)
+                        .foregroundColor(.secondary)
+                    Text(String(format: "Max: %.1f %@", maxValue, unit))
+                        .font(.caption)
+                        .foregroundColor(.secondary)
+                }
+            }
+            
+            Chart {
+                ForEach(Array(samples.enumerated()), id: \.element.id) { index, sample in
+                    LineMark(
+                        x: .value("Sample", index),
+                        y: .value("Value", sample.value)
+                    )
+                    .interpolationMethod(.monotone)
+                    .foregroundStyle(color)
+                    
+                    AreaMark(
+                        x: .value("Sample", index),
+                        y: .value("Value", sample.value)
+                    )
+                    .interpolationMethod(.monotone)
+                    .foregroundStyle(
+                        LinearGradient(
+                            colors: [color.opacity(0.35), color.opacity(0.05)],
+                            startPoint: .top,
+                            endPoint: .bottom
+                        )
+                    )
+                }
+            }
+            .chartYScale(domain: 0...(maxY ?? max(1.0, maxValue * 1.15)))
+            .chartXAxis(.hidden)
+            .frame(height: 120)
+        }
+        .padding(14)
+        .background(Color(NSColor.controlBackgroundColor))
+        .cornerRadius(10)
+    }
+}

Sources/UI/MenuBar/MenuBarStatusView.swift

@@ -0,0 +1,28 @@
+import SwiftUI
+
+public struct MenuBarStatusView: View {
+    public let cpuLoad: Double
+    public let memoryPercent: Double
+    
+    public init(cpuLoad: Double, memoryPercent: Double) {
+        self.cpuLoad = cpuLoad
+        self.memoryPercent = memoryPercent
+    }
+    
+    public var body: some View {
+        HStack(spacing: 5) {
+            Image(systemName: "cpu")
+                .font(.system(size: 11))
+            Text(String(format: "%.0f%%", cpuLoad))
+                .font(.system(size: 11, weight: .medium, design: .monospaced))
+            
+            Text("•")
+                .foregroundColor(.secondary)
+            
+            Image(systemName: "memorychip")
+                .font(.system(size: 11))
+            Text(String(format: "%.0f%%", memoryPercent))
+                .font(.system(size: 11, weight: .medium, design: .monospaced))
+        }
+    }
+}

Sources/UI/MenuBar/QuickGlancePopoverView.swift

@@ -0,0 +1,134 @@
+import SwiftUI
+
+public struct QuickGlancePopoverView: View {
+    var store: SystemTelemetryStore
+    
+    public init(store: SystemTelemetryStore) {
+        self.store = store
+    }
+    
+    public var body: some View {
+        VStack(alignment: .leading, spacing: 14) {
+            // Header
+            HStack {
+                Label("MacMonitor", systemImage: "macmini")
+                    .font(.headline)
+                Spacer()
+                Button {
+                    NSApp.activate(ignoringOtherApps: true)
+                    if let window = NSApp.windows.first(where: { $0.canBecomeMain }) {
+                        window.makeKeyAndOrderFront(nil)
+                    }
+                } label: {
+                    Image(systemName: "arrow.up.right.square")
+                        .foregroundColor(.secondary)
+                }
+                .buttonStyle(.plain)
+                .help("Open Main Window")
+            }
+            
+            Divider()
+            
+            // Core Metrics Grid
+            VStack(spacing: 8) {
+                glanceRow(
+                    icon: "cpu",
+                    title: "CPU Activity",
+                    value: String(format: "%.1f%%", store.cpuLoad.totalLoad),
+                    subtitle: "\(store.logicalCpuCount) Cores"
+                )
+                
+                glanceRow(
+                    icon: "memorychip",
+                    title: "Memory",
+                    value: String(format: "%.1f%%", store.memory.utilizationPercentage),
+                    subtitle: "\(formatBytes(store.memory.usedBytes)) / \(formatBytes(store.memory.totalBytes))"
+                )
+                
+                glanceRow(
+                    icon: "thermometer.medium",
+                    title: "Thermals",
+                    value: String(format: "%.1f°C", store.cpuThermal.packageTemperature),
+                    subtitle: "Fans: \(store.fans.map { "\(Int($0.currentRPM)) RPM" }.joined(separator: ", "))"
+                )
+                
+                glanceRow(
+                    icon: "bolt.fill",
+                    title: "Power",
+                    value: String(format: "%.1f W", store.power.systemTotalWatts),
+                    subtitle: store.batteryHealth.isCharging ? "Charging (\(Int(store.batteryHealth.healthPercent))%)" : "Battery (\(Int(store.batteryHealth.healthPercent))%)"
+                )
+                
+                glanceRow(
+                    icon: "network",
+                    title: "Network",
+                    value: "↓ \(formatBps(totalDownloadBps)) / ↑ \(formatBps(totalUploadBps))",
+                    subtitle: "\(store.networkBandwidth.count) active interfaces"
+                )
+            }
+            
+            Divider()
+            
+            // Footer action
+            HStack {
+                Text("Last updated: \(store.lastUpdateTimestamp.formatted(date: .omitted, time: .standard))")
+                    .font(.caption2)
+                    .foregroundColor(.secondary)
+                Spacer()
+                Button("Quit") {
+                    NSApplication.shared.terminate(nil)
+                }
+                .font(.caption)
+            }
+        }
+        .padding(14)
+        .frame(width: 320)
+    }
+    
+    private var totalDownloadBps: Double {
+        store.networkBandwidth.reduce(0.0) { $0 + $1.downloadBps }
+    }
+    
+    private var totalUploadBps: Double {
+        store.networkBandwidth.reduce(0.0) { $0 + $1.uploadBps }
+    }
+    
+    private func glanceRow(icon: String, title: String, value: String, subtitle: String) -> some View {
+        HStack {
+            Image(systemName: icon)
+                .frame(width: 18)
+                .foregroundColor(.accentColor)
+            VStack(alignment: .leading, spacing: 2) {
+                Text(title)
+                    .font(.caption)
+                    .foregroundColor(.secondary)
+                Text(subtitle)
+                    .font(.caption2)
+                    .foregroundColor(.secondary)
+                    .lineLimit(1)
+            }
+            Spacer()
+            Text(value)
+                .font(.subheadline)
+                .fontWeight(.semibold)
+                .fontDesign(.monospaced)
+        }
+    }
+    
+    private func formatBytes(_ bytes: UInt64) -> String {
+        let formatter = ByteCountFormatter()
+        formatter.allowedUnits = [.useAll]
+        formatter.countStyle = .memory
+        return formatter.string(fromByteCount: Int64(bytes))
+    }
+    
+    private func formatBps(_ bps: Double) -> String {
+        if bps < 1024 {
+            return String(format: "%.0f B/s", bps)
+        } else if bps < 1024 * 1024 {
+            return String(format: "%.1f KB/s", bps / 1024)
+        } else {
+            return String(format: "%.2f MB/s", bps / (1024 * 1024))
+        }
+    }
+}

Tests/MMDisplayTests.swift

@@ -0,0 +1,46 @@
+import XCTest
+@testable import MacMonitor
+
+final class MMDisplayTests: XCTestCase {
+    
+    func testDisplayManagerActiveDisplays() {
+        let manager = MMDisplayManager.shared()
+        XCTAssertNotNil(manager, "MMDisplayManager instance should not be nil")
+        
+        let displays = manager.activeDisplays()
+        XCTAssertNotNil(displays, "Active displays array should not be nil")
+        // In CI or headless/headless VM or real Mac, online display list can be checked
+        for display in displays {
+            XCTAssertGreaterThan(display.displayID, 0)
+            XCTAssertFalse(display.name.isEmpty)
+            if display.isOnline {
+                XCTAssertGreaterThan(display.width, 0)
+                XCTAssertGreaterThan(display.height, 0)
+            }
+        }
+    }
+    
+    func testDisplayInfoInitialization() {
+        let info = MMDisplayInfo(
+            displayID: 1001,
+            name: "Test Display",
+            isBuiltin: true,
+            isMain: true,
+            isOnline: true,
+            width: 2560,
+            height: 1600,
+            refreshRate: 60.0,
+            brightness: 0.75
+        )
+        
+        XCTAssertEqual(info.displayID, 1001)
+        XCTAssertEqual(info.name, "Test Display")
+        XCTAssertTrue(info.isBuiltin)
+        XCTAssertTrue(info.isMain)
+        XCTAssertTrue(info.isOnline)
+        XCTAssertEqual(info.width, 2560)
+        XCTAssertEqual(info.height, 1600)
+        XCTAssertEqual(info.refreshRate, 60.0)
+        XCTAssertEqual(info.brightness, 0.75, accuracy: 0.001)
+    }
+}

Tests/MMHistoryTests.swift

@@ -0,0 +1,54 @@
+import XCTest
+@testable import MacMonitor
+
+final class MMHistoryTests: XCTestCase {
+    
+    func testRollingRingBufferCapacityAndEviction() {
+        let buffer = RollingRingBuffer<Double>(capacity: 3)
+        XCTAssertEqual(buffer.count, 0)
+        
+        buffer.append(10.0)
+        buffer.append(20.0)
+        XCTAssertEqual(buffer.count, 2)
+        XCTAssertEqual(buffer.samples.map(\.value), [10.0, 20.0])
+        
+        buffer.append(30.0)
+        XCTAssertEqual(buffer.count, 3)
+        XCTAssertEqual(buffer.samples.map(\.value), [10.0, 20.0, 30.0])
+        
+        // 4th append should evict oldest (10.0)
+        buffer.append(40.0)
+        XCTAssertEqual(buffer.count, 3)
+        XCTAssertEqual(buffer.samples.map(\.value), [20.0, 30.0, 40.0])
+        
+        buffer.clear()
+        XCTAssertEqual(buffer.count, 0)
+        XCTAssertTrue(buffer.samples.isEmpty)
+    }
+    
+    func testTelemetryHistoryStoreRecord() {
+        let store = TelemetryHistoryStore()
+        let snapshot = TelemetrySnapshotRecord(
+            cpuLoad: 25.5,
+            memoryUsedPercent: 62.1,
+            networkInBps: 1024.0,
+            networkOutBps: 2048.0,
+            diskReadBps: 512.0,
+            diskWriteBps: 1024.0,
+            cpuTemp: 55.0,
+            systemPowerWatts: 18.5
+        )
+        store.record(snapshot: snapshot)
+        
+        XCTAssertEqual(store.sampleCounter, 1)
+        XCTAssertEqual(store.cpuHistory.count, 1)
+        XCTAssertEqual(store.cpuHistory.samples.first?.value, 25.5)
+        XCTAssertEqual(store.memoryHistory.samples.first?.value, 62.1)
+        XCTAssertEqual(store.networkInHistory.samples.first?.value, 1024.0)
+        XCTAssertEqual(store.networkOutHistory.samples.first?.value, 2048.0)
+        XCTAssertEqual(store.diskReadHistory.samples.first?.value, 512.0)
+        XCTAssertEqual(store.diskWriteHistory.samples.first?.value, 1024.0)
+        XCTAssertEqual(store.cpuTempHistory.samples.first?.value, 55.0)
+        XCTAssertEqual(store.powerHistory.samples.first?.value, 18.5)
+    }
+}

Tests/MMMenuBarTests.swift

@@ -0,0 +1,18 @@
+import XCTest
+import SwiftUI
+@testable import MacMonitor
+
+final class MMMenuBarTests: XCTestCase {
+    
+    func testMenuBarStatusViewInitialization() {
+        let view = MenuBarStatusView(cpuLoad: 24.5, memoryPercent: 55.0)
+        XCTAssertEqual(view.cpuLoad, 24.5)
+        XCTAssertEqual(view.memoryPercent, 55.0)
+    }
+    
+    func testQuickGlancePopoverViewInitialization() {
+        let store = SystemTelemetryStore.shared
+        let view = QuickGlancePopoverView(store: store)
+        XCTAssertNotNil(view)
+    }
+}