diff --git a/tests/clipboard-functionality.test.js b/tests/clipboard-functionality.test.js
new file mode 100644
index 0000000..ffdf9bd
--- /dev/null
+++ b/tests/clipboard-functionality.test.js
@@ -0,0 +1,480 @@
+/**
+ * Comprehensive test suite for clipboard functionality
+ * Tests clipboard API availability detection, operations with different backgrounds,
+ * error handling, and preference persistence
+ */
+
+// Mock ScreenshotSelector class for testing
+class MockScreenshotSelector {
+  constructor() {
+    this.copyToClipboard = true;
+    this.background = 'black';
+  }
+
+  checkClipboardAPIAvailability() {
+    if (!global.navigator.clipboard) {
+      return { available: false, reason: 'Clipboard API not available in this browser' };
+    }
+    if (!global.window.ClipboardItem) {
+      return { available: false, reason: 'ClipboardItem not supported in this browser' };
+    }
+    if (!global.window.isSecureContext) {
+      return { available: false, reason: 'Clipboard API requires a secure context (HTTPS)' };
+    }
+    if (!global.navigator.clipboard.write) {
+      return { available: false, reason: 'Clipboard write functionality not available' };
+    }
+    return { available: true };
+  }
+
+  async copyCanvasToClipboard(canvas) {
+    try {
+      const availability = this.checkClipboardAPIAvailability();
+      if (!availability.available) {
+        return { success: false, error: availability.reason, errorType: 'api_unavailable' };
+      }
+
+      const blob = await Promise.race([
+        new Promise((resolve, reject) => {
+          canvas.toBlob((blob) => {
+            if (blob) resolve(blob);
+            else reject(new Error('Canvas to blob conversion returned null'));
+          }, 'image/png');
+        }),
+        new Promise((_, reject) => 
+          setTimeout(() => reject(new Error('Canvas to blob conversion timed out')), 10000)
+        )
+      ]);
+
+      const maxBlobSize = 50 * 1024 * 1024;
+      if (blob.size > maxBlobSize) {
+        return {
+          success: false,
+          error: `Image too large for clipboard (${Math.round(blob.size / 1024 / 1024)}MB). Try capturing a smaller area.`,
+          errorType: 'size_limit'
+        };
+      }
+
+      let clipboardItem;
+      try {
+        clipboardItem = new global.window.ClipboardItem({ 'image/png': blob });
+      } catch (clipboardItemError) {
+        return {
+          success: false,
+          error: 'Failed to create clipboard item. Your browser may not support image clipboard operations.',
+          errorType: 'clipboard_item_creation'
+        };
+      }
+
+      await Promise.race([
+        global.navigator.clipboard.write([clipboardItem]),
+        new Promise((_, reject) => 
+          setTimeout(() => reject(new Error('Clipboard write timed out')), 5000)
+        )
+      ]);
+
+      return { success: true };
+    } catch (error) {
+      if (error.name === 'NotAllowedError') {
+        return { success: false, error: 'Permission denied', errorType: 'permission_denied' };
+      } else if (error.name === 'SecurityError') {
+        return { success: false, error: 'Security error', errorType: 'security_error' };
+      } else if (error.message.includes('Canvas to blob conversion returned null')) {
+        return { success: false, error: error.message, errorType: 'canvas_conversion' };
+      } else if (error.message.includes('ClipboardItem creation failed')) {
+        return { success: false, error: error.message, errorType: 'clipboard_item_creation' };
+      } else if (error.message.includes('timed out')) {
+        return { success: false, error: error.message, errorType: 'timeout' };
+      }
+      return { success: false, error: error.message, errorType: 'unexpected' };
+    }
+  }
+
+  getClipboardErrorMessage(clipboardResult) {
+    if (!clipboardResult || !clipboardResult.error) {
+      return 'Clipboard copy failed due to unknown error.';
+    }
+
+    const errorType = clipboardResult.errorType;
+    const errorMessage = clipboardResult.error;
+
+    switch (errorType) {
+      case 'permission_denied':
+        return 'Clipboard copy failed: Permission denied. Please allow clipboard access in your browser settings.';
+      case 'not_supported':
+      case 'api_unavailable':
+        return 'Clipboard copy not available in this browser. Screenshot was still downloaded.';
+      case 'security_error':
+        return 'Clipboard copy blocked by browser security. Try using HTTPS or check site permissions.';
+      case 'size_limit':
+      case 'quota_exceeded':
+        return 'Clipboard copy failed: Image too large. Try capturing a smaller area.';
+      case 'timeout':
+        return 'Clipboard copy timed out. The image may be too large or complex.';
+      default:
+        return `Clipboard copy failed: ${errorMessage}`;
+    }
+  }
+
+  getClipboardSupportFeedback() {
+    const availability = this.checkClipboardAPIAvailability();
+    
+    if (availability.available) {
+      return {
+        supported: true,
+        message: 'Clipboard copying is available and ready to use.'
+      };
+    }
+
+    let userMessage = '';
+    if (availability.reason.includes('not available') || availability.reason.includes('not supported')) {
+      userMessage = 'Your browser doesn\'t support clipboard copying. Screenshots will still be downloaded.';
+    } else if (availability.reason.includes('secure context')) {
+      userMessage = 'Clipboard copying requires HTTPS. Screenshots will still be downloaded.';
+    } else if (availability.reason.includes('write functionality')) {
+      userMessage = 'Clipboard writing is not available. Screenshots will still be downloaded.';
+    } else {
+      userMessage = 'Clipboard copying is not available. Screenshots will still be downloaded.';
+    }
+
+    return {
+      supported: false,
+      message: userMessage
+    };
+  }
+}
+
+describe('Clipboard API Availability Detection', () => {
+  let screenshotSelector;
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    screenshotSelector = new MockScreenshotSelector();
+  });
+
+  test('should detect clipboard API availability when all APIs are present', () => {
+    global.navigator = {
+      clipboard: {
+        write: jest.fn()
+      }
+    };
+    global.window.ClipboardItem = jest.fn();
+    global.window.isSecureContext = true;
+
+    const result = screenshotSelector.checkClipboardAPIAvailability();
+    
+    expect(result.available).toBe(true);
+    expect(result.reason).toBeUndefined();
+  });
+
+  test('should detect missing navigator.clipboard', () => {
+    global.navigator = {};
+    
+    const result = screenshotSelector.checkClipboardAPIAvailability();
+    
+    expect(result.available).toBe(false);
+    expect(result.reason).toBe('Clipboard API not available in this browser');
+  });
+
+  test('should detect missing ClipboardItem', () => {
+    global.navigator = {
+      clipboard: { write: jest.fn() }
+    };
+    global.window.ClipboardItem = undefined;
+    
+    const result = screenshotSelector.checkClipboardAPIAvailability();
+    
+    expect(result.available).toBe(false);
+    expect(result.reason).toBe('ClipboardItem not supported in this browser');
+  });
+
+  test('should detect insecure context', () => {
+    global.navigator = {
+      clipboard: { write: jest.fn() }
+    };
+    global.window.ClipboardItem = jest.fn();
+    global.window.isSecureContext = false;
+    
+    const result = screenshotSelector.checkClipboardAPIAvailability();
+    
+    expect(result.available).toBe(false);
+    expect(result.reason).toBe('Clipboard API requires a secure context (HTTPS)');
+  });
+
+  test('should detect missing clipboard.write', () => {
+    global.navigator = {
+      clipboard: {}
+    };
+    global.window.ClipboardItem = jest.fn();
+    global.window.isSecureContext = true;
+    
+    const result = screenshotSelector.checkClipboardAPIAvailability();
+    
+    expect(result.available).toBe(false);
+    expect(result.reason).toBe('Clipboard write functionality not available');
+  });
+});
+
+describe('Clipboard Operations with Different Background Settings', () => {
+  let screenshotSelector;
+  let mockCanvas;
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    
+    global.navigator = {
+      clipboard: {
+        write: jest.fn().mockResolvedValue()
+      }
+    };
+    global.window.ClipboardItem = jest.fn();
+    global.window.isSecureContext = true;
+
+    mockCanvas = {
+      toBlob: jest.fn((callback, format) => {
+        const mockBlob = new Blob(['mock image data'], { type: format });
+        callback(mockBlob);
+      }),
+      toDataURL: jest.fn(() => 'data:image/png;base64,mockdata')
+    };
+
+    screenshotSelector = new MockScreenshotSelector();
+  });
+
+  test('should copy to clipboard with transparent background', async () => {
+    screenshotSelector.background = 'transparent';
+    screenshotSelector.copyToClipboard = true;
+
+    const result = await screenshotSelector.copyCanvasToClipboard(mockCanvas);
+
+    expect(result.success).toBe(true);
+    expect(mockCanvas.toBlob).toHaveBeenCalledWith(expect.any(Function), 'image/png');
+    expect(global.navigator.clipboard.write).toHaveBeenCalled();
+  });
+
+  test('should copy to clipboard with black background', async () => {
+    screenshotSelector.background = 'black';
+    screenshotSelector.copyToClipboard = true;
+
+    const result = await screenshotSelector.copyCanvasToClipboard(mockCanvas);
+
+    expect(result.success).toBe(true);
+    expect(mockCanvas.toBlob).toHaveBeenCalledWith(expect.any(Function), 'image/png');
+    expect(global.navigator.clipboard.write).toHaveBeenCalled();
+  });
+
+  test('should copy to clipboard with white background', async () => {
+    screenshotSelector.background = 'white';
+    screenshotSelector.copyToClipboard = true;
+
+    const result = await screenshotSelector.copyCanvasToClipboard(mockCanvas);
+
+    expect(result.success).toBe(true);
+    expect(mockCanvas.toBlob).toHaveBeenCalledWith(expect.any(Function), 'image/png');
+    expect(global.navigator.clipboard.write).toHaveBeenCalled();
+  });
+
+  test('should handle canvas to blob conversion failure', async () => {
+    mockCanvas.toBlob = jest.fn((callback) => {
+      callback(null);
+    });
+
+    const result = await screenshotSelector.copyCanvasToClipboard(mockCanvas);
+
+    expect(result.success).toBe(false);
+    expect(result.error).toBe('Canvas to blob conversion returned null');
+    expect(result.errorType).toBe('canvas_conversion');
+  });
+
+  test('should handle large blob size limit', async () => {
+    const largeMockBlob = {
+      size: 60 * 1024 * 1024,
+      type: 'image/png'
+    };
+    
+    mockCanvas.toBlob = jest.fn((callback) => {
+      callback(largeMockBlob);
+    });
+
+    const result = await screenshotSelector.copyCanvasToClipboard(mockCanvas);
+
+    expect(result.success).toBe(false);
+    expect(result.error).toContain('Image too large for clipboard');
+    expect(result.errorType).toBe('size_limit');
+  });
+});
+
+describe('Error Handling for Clipboard Operations', () => {
+  let screenshotSelector;
+  let mockCanvas;
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    
+    mockCanvas = {
+      toBlob: jest.fn((callback) => {
+        const mockBlob = new Blob(['mock data'], { type: 'image/png' });
+        callback(mockBlob);
+      })
+    };
+
+    screenshotSelector = new MockScreenshotSelector();
+  });
+
+  test('should handle permission denied errors', async () => {
+    global.navigator = {
+      clipboard: {
+        write: jest.fn().mockRejectedValue(new DOMException('Permission denied', 'NotAllowedError'))
+      }
+    };
+    global.window.ClipboardItem = jest.fn();
+    global.window.isSecureContext = true;
+
+    const result = await screenshotSelector.copyCanvasToClipboard(mockCanvas);
+
+    expect(result.success).toBe(false);
+    expect(result.errorType).toBe('permission_denied');
+    expect(result.error).toContain('Permission denied');
+  });
+
+  test('should handle security errors', async () => {
+    global.navigator = {
+      clipboard: {
+        write: jest.fn().mockRejectedValue(new DOMException('Security error', 'SecurityError'))
+      }
+    };
+    global.window.ClipboardItem = jest.fn();
+    global.window.isSecureContext = true;
+
+    const result = await screenshotSelector.copyCanvasToClipboard(mockCanvas);
+
+    expect(result.success).toBe(false);
+    expect(result.errorType).toBe('security_error');
+  });
+
+  test('should handle ClipboardItem creation failure', async () => {
+    global.navigator = {
+      clipboard: { write: jest.fn() }
+    };
+    global.window.ClipboardItem = jest.fn(() => {
+      throw new Error('ClipboardItem creation failed');
+    });
+    global.window.isSecureContext = true;
+
+    const result = await screenshotSelector.copyCanvasToClipboard(mockCanvas);
+
+    expect(result.success).toBe(false);
+    expect(result.errorType).toBe('clipboard_item_creation');
+  });
+});
+
+describe('User-Friendly Error Messages', () => {
+  let screenshotSelector;
+
+  beforeEach(() => {
+    screenshotSelector = new MockScreenshotSelector();
+  });
+
+  test('should provide user-friendly message for permission denied', () => {
+    const clipboardResult = {
+      success: false,
+      error: 'Permission denied',
+      errorType: 'permission_denied'
+    };
+
+    const message = screenshotSelector.getClipboardErrorMessage(clipboardResult);
+    
+    expect(message).toBe('Clipboard copy failed: Permission denied. Please allow clipboard access in your browser settings.');
+  });
+
+  test('should provide user-friendly message for API unavailable', () => {
+    const clipboardResult = {
+      success: false,
+      error: 'API not supported',
+      errorType: 'api_unavailable'
+    };
+
+    const message = screenshotSelector.getClipboardErrorMessage(clipboardResult);
+    
+    expect(message).toBe('Clipboard copy not available in this browser. Screenshot was still downloaded.');
+  });
+
+  test('should provide user-friendly message for size limit', () => {
+    const clipboardResult = {
+      success: false,
+      error: 'Image too large',
+      errorType: 'size_limit'
+    };
+
+    const message = screenshotSelector.getClipboardErrorMessage(clipboardResult);
+    
+    expect(message).toBe('Clipboard copy failed: Image too large. Try capturing a smaller area.');
+  });
+
+  test('should provide user-friendly message for timeout', () => {
+    const clipboardResult = {
+      success: false,
+      error: 'Operation timed out',
+      errorType: 'timeout'
+    };
+
+    const message = screenshotSelector.getClipboardErrorMessage(clipboardResult);
+    
+    expect(message).toBe('Clipboard copy timed out. The image may be too large or complex.');
+  });
+
+  test('should handle unknown error types gracefully', () => {
+    const clipboardResult = {
+      success: false,
+      error: 'Unknown error occurred',
+      errorType: 'unknown'
+    };
+
+    const message = screenshotSelector.getClipboardErrorMessage(clipboardResult);
+    
+    expect(message).toBe('Clipboard copy failed: Unknown error occurred');
+  });
+});
+
+describe('Clipboard Support Feedback', () => {
+  let screenshotSelector;
+
+  beforeEach(() => {
+    screenshotSelector = new MockScreenshotSelector();
+  });
+
+  test('should provide positive feedback when clipboard is supported', () => {
+    global.navigator = {
+      clipboard: { write: jest.fn() }
+    };
+    global.window.ClipboardItem = jest.fn();
+    global.window.isSecureContext = true;
+
+    const feedback = screenshotSelector.getClipboardSupportFeedback();
+    
+    expect(feedback.supported).toBe(true);
+    expect(feedback.message).toBe('Clipboard copying is available and ready to use.');
+  });
+
+  test('should provide helpful feedback when clipboard is not supported', () => {
+    global.navigator = {};
+
+    const feedback = screenshotSelector.getClipboardSupportFeedback();
+    
+    expect(feedback.supported).toBe(false);
+    expect(feedback.message).toBe('Your browser doesn\'t support clipboard copying. Screenshots will still be downloaded.');
+  });
+
+  test('should provide HTTPS requirement feedback', () => {
+    global.navigator = {
+      clipboard: { write: jest.fn() }
+    };
+    global.window.ClipboardItem = jest.fn();
+    global.window.isSecureContext = false;
+
+    const feedback = screenshotSelector.getClipboardSupportFeedback();
+    
+    expect(feedback.supported).toBe(false);
+    expect(feedback.message).toBe('Clipboard copying requires HTTPS. Screenshots will still be downloaded.');
+  });
+});
\ No newline at end of file
diff --git a/tests/integration-scenarios.test.js b/tests/integration-scenarios.test.js
new file mode 100644
index 0000000..2221bf7
--- /dev/null
+++ b/tests/integration-scenarios.test.js
@@ -0,0 +1,521 @@
+/**
+ * Integration test suite for clipboard functionality across different scenarios
+ * Tests end-to-end workflows combining clipboard operations with various settings
+ */
+
+// Mock Chrome APIs
+global.chrome = {
+  storage: {
+    sync: {
+      get: jest.fn(),
+      set: jest.fn()
+    }
+  },
+  runtime: {
+    sendMessage: jest.fn()
+  },
+  tabs: {
+    query: jest.fn(),
+    sendMessage: jest.fn()
+  }
+};
+
+// Mock DOM APIs
+global.document = {
+  createElement: jest.fn(() => ({
+    style: {},
+    classList: { add: jest.fn(), remove: jest.fn() },
+    appendChild: jest.fn(),
+    click: jest.fn(),
+    addEventListener: jest.fn(),
+    removeEventListener: jest.fn(),
+    innerHTML: '',
+    textContent: '',
+    id: '',
+    className: ''
+  })),
+  head: { appendChild: jest.fn() },
+  body: { appendChild: jest.fn() },
+  addEventListener: jest.fn(),
+  removeEventListener: jest.fn(),
+  querySelectorAll: jest.fn(() => []),
+  getElementById: jest.fn()
+};
+
+global.window = {
+  getComputedStyle: jest.fn(() => ({})),
+  devicePixelRatio: 2,
+  isSecureContext: true,
+  CSS: { escape: jest.fn(str => str) },
+  setTimeout: jest.fn((fn, delay) => {
+    if (delay === 0) fn();
+    return 1;
+  })
+};
+
+// Mock html2canvas
+global.html2canvas = jest.fn();
+
+describe('Integration Scenarios - Clipboard with Different Backgrounds', () => {
+  let screenshotSelector;
+  let mockElement;
+  let mockCanvas;
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    
+    // Mock element to capture
+    mockElement = {
+      classList: {
+        add: jest.fn(),
+        remove: jest.fn()
+      },
+      style: {},
+      getBoundingClientRect: () => ({ left: 0, top: 0, width: 100, height: 100 }),
+      scrollHeight: 100,
+      clientHeight: 100,
+      scrollWidth: 100,
+      clientWidth: 100,
+      children: [],
+      parentNode: { children: [] }
+    };
+
+    // Mock canvas
+    mockCanvas = {
+      toBlob: jest.fn((callback, format) => {
+        const mockBlob = new Blob(['mock image data'], { type: format });
+        Object.defineProperty(mockBlob, 'size', { value: 1024 }); // 1KB
+        callback(mockBlob);
+      }),
+      toDataURL: jest.fn(() => 'data:image/png;base64,mockdata')
+    };
+
+    global.html2canvas = jest.fn().mockResolvedValue(mockCanvas);
+
+    // Mock full clipboard API support
+    global.navigator = {
+      clipboard: {
+        write: jest.fn().mockResolvedValue()
+      }
+    };
+    global.window.ClipboardItem = jest.fn();
+
+    // Import ScreenshotSelector (simplified for testing)
+    const ScreenshotSelector = class {
+      constructor() {
+        this.isActive = false;
+        this.background = 'black';
+        this.copyToClipboard = true;
+        this.overlay = null;
+      }
+
+      async init(background = 'black', copyToClipboard = true) {
+        this.background = background;
+        this.copyToClipboard = copyToClipboard;
+        this.isActive = true;
+        this.createUI();
+      }
+
+      createUI() {
+        this.overlay = global.document.createElement('div');
+        global.document.body.appendChild(this.overlay);
+      }
+
+      checkClipboardAPIAvailability() {
+        if (!global.navigator.clipboard) {
+          return { available: false, reason: 'Clipboard API not available in this browser' };
+        }
+        if (!global.window.ClipboardItem) {
+          return { available: false, reason: 'ClipboardItem not supported in this browser' };
+        }
+        if (!global.window.isSecureContext) {
+          return { available: false, reason: 'Clipboard API requires a secure context (HTTPS)' };
+        }
+        if (!global.navigator.clipboard.write) {
+          return { available: false, reason: 'Clipboard write functionality not available' };
+        }
+        return { available: true };
+      }
+
+      async copyCanvasToClipboard(canvas) {
+        try {
+          const availability = this.checkClipboardAPIAvailability();
+          if (!availability.available) {
+            return { success: false, error: availability.reason, errorType: 'api_unavailable' };
+          }
+
+          const blob = await new Promise((resolve, reject) => {
+            canvas.toBlob((blob) => {
+              if (blob) resolve(blob);
+              else reject(new Error('Canvas to blob conversion returned null'));
+            }, 'image/png');
+          });
+
+          const maxBlobSize = 50 * 1024 * 1024;
+          if (blob.size > maxBlobSize) {
+            return {
+              success: false,
+              error: `Image too large for clipboard (${Math.round(blob.size / 1024 / 1024)}MB)`,
+              errorType: 'size_limit'
+            };
+          }
+
+          const clipboardItem = new global.window.ClipboardItem({ 'image/png': blob });
+          await global.navigator.clipboard.write([clipboardItem]);
+
+          return { success: true };
+        } catch (error) {
+          if (error.name === 'NotAllowedError') {
+            return { success: false, error: 'Permission denied', errorType: 'permission_denied' };
+          }
+          return { success: false, error: error.message, errorType: 'unexpected' };
+        }
+      }
+
+      async captureElement(element) {
+        try {
+          // Generate canvas with background-specific settings
+          const canvas = await global.html2canvas(element, {
+            backgroundColor: this.background === 'transparent' ? null :
+                           this.background === 'white' ? '#ffffff' : '#000000',
+            useCORS: true,
+            allowTaint: false
+          });
+
+          // Always download first
+          const link = global.document.createElement('a');
+          link.href = canvas.toDataURL('image/png');
+          link.download = `screenshot-${new Date().toISOString().slice(0, 19).replace(/[:.]/g, '-')}.png`;
+          link.click();
+
+          // Handle clipboard if enabled
+          let clipboardResult = null;
+          if (this.copyToClipboard) {
+            clipboardResult = await this.copyCanvasToClipboard(canvas);
+          }
+
+          // Update UI based on results
+          let successMessage = 'Screenshot downloaded successfully!';
+          if (this.copyToClipboard && clipboardResult && clipboardResult.success) {
+            successMessage = 'Screenshot downloaded and copied to clipboard!';
+          } else if (this.copyToClipboard && clipboardResult && !clipboardResult.success) {
+            successMessage = `Screenshot downloaded successfully! Clipboard copy failed: ${clipboardResult.error}`;
+          }
+
+          this.overlay.innerHTML = `<div>${successMessage}</div>`;
+          
+          return {
+            success: true,
+            downloadSuccess: true,
+            clipboardResult: clipboardResult,
+            message: successMessage
+          };
+
+        } catch (error) {
+          this.overlay.innerHTML = `<div>Screenshot failed: ${error.message}</div>`;
+          return {
+            success: false,
+            error: error.message
+          };
+        }
+      }
+    };
+
+    screenshotSelector = new ScreenshotSelector();
+  });
+
+  test('should capture with transparent background and copy to clipboard', async () => {
+    await screenshotSelector.init('transparent', true);
+    
+    const result = await screenshotSelector.captureElement(mockElement);
+
+    expect(global.html2canvas).toHaveBeenCalledWith(mockElement, expect.objectContaining({
+      backgroundColor: null, // Transparent background
+      useCORS: true,
+      allowTaint: false
+    }));
+
+    expect(result.success).toBe(true);
+    expect(result.downloadSuccess).toBe(true);
+    expect(result.clipboardResult.success).toBe(true);
+    expect(result.message).toBe('Screenshot downloaded and copied to clipboard!');
+  });
+
+  test('should capture with black background and copy to clipboard', async () => {
+    await screenshotSelector.init('black', true);
+    
+    const result = await screenshotSelector.captureElement(mockElement);
+
+    expect(global.html2canvas).toHaveBeenCalledWith(mockElement, expect.objectContaining({
+      backgroundColor: '#000000', // Black background
+      useCORS: true,
+      allowTaint: false
+    }));
+
+    expect(result.success).toBe(true);
+    expect(result.clipboardResult.success).toBe(true);
+    expect(result.message).toBe('Screenshot downloaded and copied to clipboard!');
+  });
+
+  test('should capture with white background and copy to clipboard', async () => {
+    await screenshotSelector.init('white', true);
+    
+    const result = await screenshotSelector.captureElement(mockElement);
+
+    expect(global.html2canvas).toHaveBeenCalledWith(mockElement, expect.objectContaining({
+      backgroundColor: '#ffffff', // White background
+      useCORS: true,
+      allowTaint: false
+    }));
+
+    expect(result.success).toBe(true);
+    expect(result.clipboardResult.success).toBe(true);
+    expect(result.message).toBe('Screenshot downloaded and copied to clipboard!');
+  });
+
+  test('should capture without clipboard when disabled', async () => {
+    await screenshotSelector.init('black', false);
+    
+    const result = await screenshotSelector.captureElement(mockElement);
+
+    expect(result.success).toBe(true);
+    expect(result.downloadSuccess).toBe(true);
+    expect(result.clipboardResult).toBe(null); // No clipboard operation attempted
+    expect(result.message).toBe('Screenshot downloaded successfully!');
+    expect(global.navigator.clipboard.write).not.toHaveBeenCalled();
+  });
+
+  test('should handle clipboard failure gracefully while maintaining download', async () => {
+    // Mock clipboard failure
+    global.navigator.clipboard.write.mockRejectedValue(new DOMException('Permission denied', 'NotAllowedError'));
+    
+    await screenshotSelector.init('black', true);
+    
+    const result = await screenshotSelector.captureElement(mockElement);
+
+    expect(result.success).toBe(true);
+    expect(result.downloadSuccess).toBe(true);
+    expect(result.clipboardResult.success).toBe(false);
+    expect(result.clipboardResult.errorType).toBe('permission_denied');
+    expect(result.message).toContain('Screenshot downloaded successfully!');
+    expect(result.message).toContain('Clipboard copy failed');
+  });
+
+  test('should handle clipboard API unavailable scenario', async () => {
+    // Mock clipboard API not available
+    global.navigator.clipboard = undefined;
+    
+    await screenshotSelector.init('transparent', true);
+    
+    const result = await screenshotSelector.captureElement(mockElement);
+
+    expect(result.success).toBe(true);
+    expect(result.downloadSuccess).toBe(true);
+    expect(result.clipboardResult.success).toBe(false);
+    expect(result.clipboardResult.errorType).toBe('api_unavailable');
+    expect(result.message).toContain('Screenshot downloaded successfully!');
+    expect(result.message).toContain('Clipboard copy failed');
+  });
+});
+
+describe('Integration Scenarios - Complete Workflow', () => {
+  let mockPopupElements;
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    
+    // Mock popup elements
+    mockPopupElements = {
+      clipboardToggle: { checked: true, addEventListener: jest.fn() },
+      backgroundSelect: { value: 'black', addEventListener: jest.fn() },
+      startButton: { addEventListener: jest.fn(), style: { display: 'block' } },
+      status: { textContent: '', className: '', style: { display: 'none' } }
+    };
+
+    global.document.getElementById = jest.fn((id) => {
+      switch (id) {
+        case 'clipboard-toggle': return mockPopupElements.clipboardToggle;
+        case 'background-select': return mockPopupElements.backgroundSelect;
+        case 'start-selector': return mockPopupElements.startButton;
+        case 'status': return mockPopupElements.status;
+        default: return null;
+      }
+    });
+
+    // Mock Chrome APIs
+    global.chrome.storage.sync.get.mockResolvedValue({
+      backgroundPreference: 'black',
+      copyToClipboard: true
+    });
+    global.chrome.tabs.query.mockResolvedValue([{ id: 123, url: 'https://example.com' }]);
+    global.chrome.tabs.sendMessage.mockResolvedValue();
+  });
+
+  test('should complete full workflow from popup to content script', async () => {
+    let startButtonCallback;
+    mockPopupElements.startButton.addEventListener = jest.fn((event, callback) => {
+      if (event === 'click') startButtonCallback = callback;
+    });
+
+    // Simulate popup initialization
+    const popupScript = `
+      document.addEventListener('DOMContentLoaded', async () => {
+        const backgroundSelect = document.getElementById('background-select');
+        const clipboardToggle = document.getElementById('clipboard-toggle');
+        const startBtn = document.getElementById('start-selector');
+        
+        // Load preferences
+        const saved = await chrome.storage.sync.get(['backgroundPreference', 'copyToClipboard']);
+        if (saved.backgroundPreference) {
+          backgroundSelect.value = saved.backgroundPreference;
+        }
+        clipboardToggle.checked = saved.copyToClipboard !== undefined ? saved.copyToClipboard : true;
+        
+        // Start selector
+        startBtn.addEventListener('click', async () => {
+          const [tab] = await chrome.tabs.query({ active: true, currentWindow: true });
+          
+          await chrome.tabs.sendMessage(tab.id, {
+            action: 'startSelector',
+            background: backgroundSelect.value,
+            copyToClipboard: clipboardToggle.checked
+          });
+        });
+      });
+    `;
+
+    // Execute popup initialization
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      eval(popupScript);
+    });
+
+    // Verify preferences were loaded
+    expect(mockPopupElements.backgroundSelect.value).toBe('black');
+    expect(mockPopupElements.clipboardToggle.checked).toBe(true);
+
+    // Simulate start button click
+    await startButtonCallback();
+
+    // Verify message was sent to content script with correct parameters
+    expect(global.chrome.tabs.sendMessage).toHaveBeenCalledWith(123, {
+      action: 'startSelector',
+      background: 'black',
+      copyToClipboard: true
+    });
+  });
+
+  test('should handle preference changes and persist them', async () => {
+    let clipboardChangeCallback;
+    let backgroundChangeCallback;
+
+    mockPopupElements.clipboardToggle.addEventListener = jest.fn((event, callback) => {
+      if (event === 'change') clipboardChangeCallback = callback;
+    });
+
+    mockPopupElements.backgroundSelect.addEventListener = jest.fn((event, callback) => {
+      if (event === 'change') backgroundChangeCallback = callback;
+    });
+
+    // Initialize popup
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      
+      const popupScript = `
+        document.addEventListener('DOMContentLoaded', async () => {
+          const backgroundSelect = document.getElementById('background-select');
+          const clipboardToggle = document.getElementById('clipboard-toggle');
+          
+          backgroundSelect.addEventListener('change', () => {
+            chrome.storage.sync.set({ backgroundPreference: backgroundSelect.value });
+          });
+
+          clipboardToggle.addEventListener('change', () => {
+            chrome.storage.sync.set({ copyToClipboard: clipboardToggle.checked });
+          });
+        });
+      `;
+      eval(popupScript);
+    });
+
+    // Change background preference
+    mockPopupElements.backgroundSelect.value = 'transparent';
+    backgroundChangeCallback();
+
+    expect(global.chrome.storage.sync.set).toHaveBeenCalledWith({ backgroundPreference: 'transparent' });
+
+    // Change clipboard preference
+    mockPopupElements.clipboardToggle.checked = false;
+    clipboardChangeCallback();
+
+    expect(global.chrome.storage.sync.set).toHaveBeenCalledWith({ copyToClipboard: false });
+  });
+
+  test('should handle incompatible pages gracefully', async () => {
+    // Mock incompatible page
+    global.chrome.tabs.query.mockResolvedValue([{ 
+      id: 123, 
+      url: 'chrome://settings/' 
+    }]);
+
+    let startButtonCallback;
+    mockPopupElements.startButton.addEventListener = jest.fn((event, callback) => {
+      if (event === 'click') startButtonCallback = callback;
+    });
+
+    // Initialize popup with incompatible page handling
+    const popupScript = `
+      document.addEventListener('DOMContentLoaded', async () => {
+        const startBtn = document.getElementById('start-selector');
+        const status = document.getElementById('status');
+        
+        startBtn.addEventListener('click', async () => {
+          const [tab] = await chrome.tabs.query({ active: true, currentWindow: true });
+
+          if (tab.url.startsWith('chrome://') ||
+              tab.url.startsWith('chrome-extension://') ||
+              tab.url.startsWith('edge://') ||
+              tab.url.startsWith('about:')) {
+            status.textContent = 'Error: Cannot capture screenshots on this page type.';
+            status.className = 'status error';
+            status.style.display = 'block';
+            return;
+          }
+          
+          // Normal flow would continue here
+        });
+      });
+    `;
+
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      eval(popupScript);
+    });
+
+    // Simulate start button click on incompatible page
+    await startButtonCallback();
+
+    // Verify error message was shown
+    expect(mockPopupElements.status.textContent).toBe('Error: Cannot capture screenshots on this page type.');
+    expect(mockPopupElements.status.className).toBe('status error');
+    expect(mockPopupElements.status.style.display).toBe('block');
+
+    // Verify no message was sent to content script
+    expect(global.chrome.tabs.sendMessage).not.toHaveBeenCalled();
+  });
+});
\ No newline at end of file
diff --git a/tests/preference-persistence.test.js b/tests/preference-persistence.test.js
new file mode 100644
index 0000000..6db7941
--- /dev/null
+++ b/tests/preference-persistence.test.js
@@ -0,0 +1,414 @@
+/**
+ * Test suite for clipboard preference persistence across browser sessions
+ * Tests storage, retrieval, and default behavior of clipboard preferences
+ */
+
+// Mock Chrome APIs
+global.chrome = {
+  storage: {
+    sync: {
+      get: jest.fn(),
+      set: jest.fn()
+    }
+  },
+  runtime: {
+    sendMessage: jest.fn()
+  },
+  tabs: {
+    query: jest.fn(),
+    sendMessage: jest.fn()
+  }
+};
+
+// Mock DOM APIs
+global.document = {
+  createElement: jest.fn(() => ({
+    style: {},
+    classList: { add: jest.fn(), remove: jest.fn() },
+    appendChild: jest.fn(),
+    click: jest.fn(),
+    addEventListener: jest.fn(),
+    removeEventListener: jest.fn(),
+    id: '',
+    checked: false,
+    value: ''
+  })),
+  head: { appendChild: jest.fn() },
+  body: { appendChild: jest.fn() },
+  addEventListener: jest.fn(),
+  removeEventListener: jest.fn(),
+  querySelectorAll: jest.fn(() => []),
+  getElementById: jest.fn()
+};
+
+global.window = {
+  close: jest.fn(),
+  setTimeout: jest.fn((fn) => fn())
+};
+
+describe('Clipboard Preference Persistence', () => {
+  let mockClipboardToggle;
+  let mockBackgroundSelect;
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    
+    // Mock DOM elements
+    mockClipboardToggle = {
+      checked: false,
+      addEventListener: jest.fn()
+    };
+    
+    mockBackgroundSelect = {
+      value: 'black',
+      addEventListener: jest.fn()
+    };
+
+    global.document.getElementById = jest.fn((id) => {
+      switch (id) {
+        case 'clipboard-toggle':
+          return mockClipboardToggle;
+        case 'background-select':
+          return mockBackgroundSelect;
+        case 'start-selector':
+          return { addEventListener: jest.fn(), style: { display: 'block' } };
+        case 'stop-selector':
+          return { addEventListener: jest.fn(), style: { display: 'none' } };
+        case 'status':
+          return { textContent: '', className: '', style: { display: 'none' } };
+        default:
+          return null;
+      }
+    });
+  });
+
+  test('should load default clipboard preference when no saved preference exists', async () => {
+    // Mock storage returning no saved preferences
+    global.chrome.storage.sync.get.mockResolvedValue({});
+
+    // Simulate popup script loading
+    const popupScript = `
+      document.addEventListener('DOMContentLoaded', async () => {
+        const clipboardToggle = document.getElementById('clipboard-toggle');
+        const saved = await chrome.storage.sync.get(['backgroundPreference', 'copyToClipboard']);
+        clipboardToggle.checked = saved.copyToClipboard !== undefined ? saved.copyToClipboard : true;
+      });
+    `;
+
+    // Execute the popup script logic
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      eval(popupScript);
+    });
+
+    expect(global.chrome.storage.sync.get).toHaveBeenCalledWith(['backgroundPreference', 'copyToClipboard']);
+    expect(mockClipboardToggle.checked).toBe(true); // Default should be true
+  });
+
+  test('should load saved clipboard preference when it exists', async () => {
+    // Mock storage returning saved preferences
+    global.chrome.storage.sync.get.mockResolvedValue({
+      backgroundPreference: 'white',
+      copyToClipboard: false
+    });
+
+    // Simulate popup script loading
+    const popupScript = `
+      document.addEventListener('DOMContentLoaded', async () => {
+        const clipboardToggle = document.getElementById('clipboard-toggle');
+        const saved = await chrome.storage.sync.get(['backgroundPreference', 'copyToClipboard']);
+        clipboardToggle.checked = saved.copyToClipboard !== undefined ? saved.copyToClipboard : true;
+      });
+    `;
+
+    // Execute the popup script logic
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      eval(popupScript);
+    });
+
+    expect(mockClipboardToggle.checked).toBe(false); // Should load saved value
+  });
+
+  test('should save clipboard preference when toggle is changed', async () => {
+    let changeCallback;
+    mockClipboardToggle.addEventListener = jest.fn((event, callback) => {
+      if (event === 'change') {
+        changeCallback = callback;
+      }
+    });
+
+    // Simulate popup script initialization
+    const popupScript = `
+      document.addEventListener('DOMContentLoaded', async () => {
+        const clipboardToggle = document.getElementById('clipboard-toggle');
+        clipboardToggle.addEventListener('change', () => {
+          chrome.storage.sync.set({ copyToClipboard: clipboardToggle.checked });
+        });
+      });
+    `;
+
+    // Execute the popup script logic
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      eval(popupScript);
+    });
+
+    // Simulate user toggling the checkbox
+    mockClipboardToggle.checked = true;
+    changeCallback();
+
+    expect(global.chrome.storage.sync.set).toHaveBeenCalledWith({ copyToClipboard: true });
+  });
+
+  test('should persist clipboard preference across multiple sessions', async () => {
+    // Simulate first session - user enables clipboard
+    global.chrome.storage.sync.get.mockResolvedValueOnce({});
+    
+    let firstSessionChangeCallback;
+    mockClipboardToggle.addEventListener = jest.fn((event, callback) => {
+      if (event === 'change') {
+        firstSessionChangeCallback = callback;
+      }
+    });
+
+    // First session initialization
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      
+      const popupScript = `
+        document.addEventListener('DOMContentLoaded', async () => {
+          const clipboardToggle = document.getElementById('clipboard-toggle');
+          const saved = await chrome.storage.sync.get(['backgroundPreference', 'copyToClipboard']);
+          clipboardToggle.checked = saved.copyToClipboard !== undefined ? saved.copyToClipboard : true;
+          
+          clipboardToggle.addEventListener('change', () => {
+            chrome.storage.sync.set({ copyToClipboard: clipboardToggle.checked });
+          });
+        });
+      `;
+      eval(popupScript);
+    });
+
+    // User disables clipboard in first session
+    mockClipboardToggle.checked = false;
+    firstSessionChangeCallback();
+
+    expect(global.chrome.storage.sync.set).toHaveBeenCalledWith({ copyToClipboard: false });
+
+    // Simulate second session - should load the saved preference
+    jest.clearAllMocks();
+    global.chrome.storage.sync.get.mockResolvedValueOnce({
+      copyToClipboard: false
+    });
+
+    // Reset mock element
+    mockClipboardToggle.checked = true; // Reset to opposite of expected
+
+    // Second session initialization
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      
+      const popupScript = `
+        document.addEventListener('DOMContentLoaded', async () => {
+          const clipboardToggle = document.getElementById('clipboard-toggle');
+          const saved = await chrome.storage.sync.get(['backgroundPreference', 'copyToClipboard']);
+          clipboardToggle.checked = saved.copyToClipboard !== undefined ? saved.copyToClipboard : true;
+        });
+      `;
+      eval(popupScript);
+    });
+
+    expect(mockClipboardToggle.checked).toBe(false); // Should load saved preference from first session
+  });
+
+  test('should handle storage errors gracefully', async () => {
+    // Mock storage error
+    global.chrome.storage.sync.get.mockRejectedValue(new Error('Storage error'));
+
+    let errorOccurred = false;
+    
+    try {
+      const popupScript = `
+        document.addEventListener('DOMContentLoaded', async () => {
+          try {
+            const clipboardToggle = document.getElementById('clipboard-toggle');
+            const saved = await chrome.storage.sync.get(['backgroundPreference', 'copyToClipboard']);
+            clipboardToggle.checked = saved.copyToClipboard !== undefined ? saved.copyToClipboard : true;
+          } catch (error) {
+            // Should fall back to default behavior
+            const clipboardToggle = document.getElementById('clipboard-toggle');
+            clipboardToggle.checked = true; // Default value
+          }
+        });
+      `;
+
+      await new Promise(resolve => {
+        global.document.addEventListener = jest.fn((event, callback) => {
+          if (event === 'DOMContentLoaded') {
+            callback();
+            resolve();
+          }
+        });
+        eval(popupScript);
+      });
+    } catch (error) {
+      errorOccurred = true;
+    }
+
+    expect(errorOccurred).toBe(false); // Should handle error gracefully
+    expect(mockClipboardToggle.checked).toBe(true); // Should fall back to default
+  });
+
+  test('should save both background and clipboard preferences independently', async () => {
+    let clipboardChangeCallback;
+    let backgroundChangeCallback;
+
+    mockClipboardToggle.addEventListener = jest.fn((event, callback) => {
+      if (event === 'change') {
+        clipboardChangeCallback = callback;
+      }
+    });
+
+    mockBackgroundSelect.addEventListener = jest.fn((event, callback) => {
+      if (event === 'change') {
+        backgroundChangeCallback = callback;
+      }
+    });
+
+    // Initialize popup script
+    const popupScript = `
+      document.addEventListener('DOMContentLoaded', async () => {
+        const backgroundSelect = document.getElementById('background-select');
+        const clipboardToggle = document.getElementById('clipboard-toggle');
+        
+        backgroundSelect.addEventListener('change', () => {
+          chrome.storage.sync.set({ backgroundPreference: backgroundSelect.value });
+        });
+
+        clipboardToggle.addEventListener('change', () => {
+          chrome.storage.sync.set({ copyToClipboard: clipboardToggle.checked });
+        });
+      });
+    `;
+
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      eval(popupScript);
+    });
+
+    // Change background preference
+    mockBackgroundSelect.value = 'transparent';
+    backgroundChangeCallback();
+
+    expect(global.chrome.storage.sync.set).toHaveBeenCalledWith({ backgroundPreference: 'transparent' });
+
+    // Change clipboard preference
+    mockClipboardToggle.checked = false;
+    clipboardChangeCallback();
+
+    expect(global.chrome.storage.sync.set).toHaveBeenCalledWith({ copyToClipboard: false });
+
+    // Verify both calls were made independently
+    expect(global.chrome.storage.sync.set).toHaveBeenCalledTimes(2);
+  });
+
+  test('should include clipboard preference in message to content script', async () => {
+    // Mock tab query and message sending
+    global.chrome.tabs.query.mockResolvedValue([{ id: 123, url: 'https://example.com' }]);
+    global.chrome.tabs.sendMessage.mockResolvedValue();
+
+    let startButtonCallback;
+    const mockStartButton = {
+      addEventListener: jest.fn((event, callback) => {
+        if (event === 'click') {
+          startButtonCallback = callback;
+        }
+      }),
+      style: { display: 'block' }
+    };
+
+    global.document.getElementById = jest.fn((id) => {
+      switch (id) {
+        case 'start-selector':
+          return mockStartButton;
+        case 'clipboard-toggle':
+          return { checked: true }; // Clipboard enabled
+        case 'background-select':
+          return { value: 'white' };
+        case 'status':
+          return { textContent: '', className: '', style: { display: 'none' } };
+        default:
+          return mockClipboardToggle;
+      }
+    });
+
+    // Initialize popup script
+    const popupScript = `
+      document.addEventListener('DOMContentLoaded', async () => {
+        const startBtn = document.getElementById('start-selector');
+        const backgroundSelect = document.getElementById('background-select');
+        const clipboardToggle = document.getElementById('clipboard-toggle');
+        
+        startBtn.addEventListener('click', async () => {
+          const [tab] = await chrome.tabs.query({ active: true, currentWindow: true });
+          
+          await chrome.tabs.sendMessage(tab.id, {
+            action: 'startSelector',
+            background: backgroundSelect.value,
+            copyToClipboard: clipboardToggle.checked
+          });
+        });
+      });
+    `;
+
+    await new Promise(resolve => {
+      global.document.addEventListener = jest.fn((event, callback) => {
+        if (event === 'DOMContentLoaded') {
+          callback();
+          resolve();
+        }
+      });
+      eval(popupScript);
+    });
+
+    // Simulate start button click
+    await startButtonCallback();
+
+    expect(global.chrome.tabs.sendMessage).toHaveBeenCalledWith(123, {
+      action: 'startSelector',
+      background: 'white',
+      copyToClipboard: true
+    });
+  });
+});
\ No newline at end of file
diff --git a/tests/setup.js b/tests/setup.js
new file mode 100644
index 0000000..4ba46b1
--- /dev/null
+++ b/tests/setup.js
@@ -0,0 +1,237 @@
+/**
+ * Jest setup file for clipboard functionality tests
+ * Provides common mocks and utilities for all test files
+ */
+
+// Global test utilities
+global.createMockBlob = (data = 'mock data', type = 'image/png', size = 1024) => {
+  const blob = new Blob([data], { type });
+  Object.defineProperty(blob, 'size', { value: size });
+  return blob;
+};
+
+global.createMockCanvas = (width = 100, height = 100) => {
+  return {
+    width,
+    height,
+    toBlob: jest.fn((callback, format = 'image/png') => {
+      const blob = global.createMockBlob('mock canvas data', format);
+      callback(blob);
+    }),
+    toDataURL: jest.fn((format = 'image/png') => `data:${format};base64,mockcanvasdata`),
+    getContext: jest.fn(() => ({
+      drawImage: jest.fn(),
+      getImageData: jest.fn(),
+      putImageData: jest.fn()
+    }))
+  };
+};
+
+global.createMockElement = (options = {}) => {
+  return {
+    classList: {
+      add: jest.fn(),
+      remove: jest.fn(),
+      contains: jest.fn(() => false)
+    },
+    style: {},
+    getBoundingClientRect: () => ({
+      left: options.left || 0,
+      top: options.top || 0,
+      width: options.width || 100,
+      height: options.height || 100
+    }),
+    scrollHeight: options.scrollHeight || 100,
+    clientHeight: options.clientHeight || 100,
+    scrollWidth: options.scrollWidth || 100,
+    clientWidth: options.clientWidth || 100,
+    children: options.children || [],
+    parentNode: { children: options.siblings || [] },
+    tagName: options.tagName || 'DIV',
+    id: options.id || '',
+    addEventListener: jest.fn(),
+    removeEventListener: jest.fn()
+  };
+};
+
+// Mock Chrome extension APIs consistently
+global.mockChromeAPIs = () => {
+  global.chrome = {
+    storage: {
+      sync: {
+        get: jest.fn().mockResolvedValue({}),
+        set: jest.fn().mockResolvedValue()
+      }
+    },
+    runtime: {
+      sendMessage: jest.fn().mockResolvedValue(),
+      onMessage: {
+        addListener: jest.fn()
+      }
+    },
+    tabs: {
+      query: jest.fn().mockResolvedValue([{ id: 123, url: 'https://example.com' }]),
+      sendMessage: jest.fn().mockResolvedValue()
+    }
+  };
+};
+
+// Mock DOM APIs consistently
+global.mockDOMAPIs = () => {
+  global.document = {
+    createElement: jest.fn(() => ({
+      style: {},
+      classList: { add: jest.fn(), remove: jest.fn() },
+      appendChild: jest.fn(),
+      click: jest.fn(),
+      addEventListener: jest.fn(),
+      removeEventListener: jest.fn(),
+      innerHTML: '',
+      textContent: '',
+      id: '',
+      className: '',
+      checked: false,
+      value: ''
+    })),
+    head: { appendChild: jest.fn() },
+    body: { appendChild: jest.fn() },
+    addEventListener: jest.fn(),
+    removeEventListener: jest.fn(),
+    querySelectorAll: jest.fn(() => []),
+    getElementById: jest.fn(() => null)
+  };
+
+  global.window = {
+    getComputedStyle: jest.fn(() => ({})),
+    devicePixelRatio: 2,
+    isSecureContext: true,
+    CSS: { escape: jest.fn(str => str) },
+    setTimeout: jest.fn((fn, delay) => {
+      if (delay === 0) fn();
+      return 1;
+    }),
+    clearTimeout: jest.fn(),
+    close: jest.fn()
+  };
+};
+
+// Mock clipboard APIs with different scenarios
+global.mockClipboardAPI = (scenario = 'supported') => {
+  switch (scenario) {
+    case 'supported':
+      global.navigator = {
+        clipboard: {
+          write: jest.fn().mockResolvedValue()
+        }
+      };
+      global.window.ClipboardItem = jest.fn();
+      global.window.isSecureContext = true;
+      break;
+      
+    case 'no-clipboard':
+      global.navigator = {};
+      break;
+      
+    case 'no-clipboarditem':
+      global.navigator = {
+        clipboard: { write: jest.fn() }
+      };
+      global.window.ClipboardItem = undefined;
+      break;
+      
+    case 'insecure-context':
+      global.navigator = {
+        clipboard: { write: jest.fn() }
+      };
+      global.window.ClipboardItem = jest.fn();
+      global.window.isSecureContext = false;
+      break;
+      
+    case 'permission-denied':
+      global.navigator = {
+        clipboard: {
+          write: jest.fn().mockRejectedValue(new DOMException('Permission denied', 'NotAllowedError'))
+        }
+      };
+      global.window.ClipboardItem = jest.fn();
+      global.window.isSecureContext = true;
+      break;
+      
+    case 'security-error':
+      global.navigator = {
+        clipboard: {
+          write: jest.fn().mockRejectedValue(new DOMException('Security error', 'SecurityError'))
+        }
+      };
+      global.window.ClipboardItem = jest.fn();
+      global.window.isSecureContext = true;
+      break;
+  }
+};
+
+// Setup default mocks before each test
+beforeEach(() => {
+  // Clear all mocks first
+  jest.clearAllMocks();
+  
+  global.mockChromeAPIs();
+  global.mockDOMAPIs();
+  global.mockClipboardAPI('supported');
+  
+  // Mock html2canvas
+  global.html2canvas = jest.fn().mockResolvedValue(global.createMockCanvas());
+});
+
+// Cleanup after each test
+afterEach(() => {
+  jest.restoreAllMocks();
+});
+
+// Custom matchers for better test assertions
+expect.extend({
+  toHaveBeenCalledWithClipboardMessage(received, expectedBackground, expectedClipboard) {
+    const calls = received.mock.calls;
+    const matchingCall = calls.find(call => 
+      call[1] && 
+      call[1].action === 'startSelector' &&
+      call[1].background === expectedBackground &&
+      call[1].copyToClipboard === expectedClipboard
+    );
+    
+    if (matchingCall) {
+      return {
+        message: () => `Expected not to be called with clipboard message`,
+        pass: true
+      };
+    } else {
+      return {
+        message: () => `Expected to be called with clipboard message (background: ${expectedBackground}, clipboard: ${expectedClipboard})`,
+        pass: false
+      };
+    }
+  },
+  
+  toHaveClipboardResult(received, expectedSuccess, expectedErrorType) {
+    if (!received.clipboardResult) {
+      return {
+        message: () => `Expected clipboard result to exist`,
+        pass: false
+      };
+    }
+    
+    const success = received.clipboardResult.success === expectedSuccess;
+    const errorType = !expectedErrorType || received.clipboardResult.errorType === expectedErrorType;
+    
+    if (success && errorType) {
+      return {
+        message: () => `Expected clipboard result not to match`,
+        pass: true
+      };
+    } else {
+      return {
+        message: () => `Expected clipboard result (success: ${expectedSuccess}, errorType: ${expectedErrorType}), got (success: ${received.clipboardResult.success}, errorType: ${received.clipboardResult.errorType})`,
+        pass: false
+      };
+    }
+  }
+});
\ No newline at end of file