test(CopyRepoButton): add component tests (JhaSourav07#3545)

- Test rendering and initial state
- Verify clipboard API is called with correct URL
- Test success state label change
- Verify timeout reset behavior
- Test error handling for clipboard failures

All 5 test cases passing

## Description

Fixes JhaSourav07#2284 

## Pillar

- [ ] Pillar 1 — New Theme Design
- [ ]  Pillar 2 — Geometric SVG Improvement
- [ ]  Pillar 3 — Timezone Logic Optimization
- [ ]  Other (Bug fix, refactoring, docs)

## Visual Preview

## Checklist before requesting a review:

- [ ] I have read the `CONTRIBUTING.md` file.
- [ ] I have tested these changes locally
(`localhost:3000/api/streak?user=YOUR_USERNAME`).
- [ ] I have run `npm run format` and `npm run lint` locally and
resolved all errors (CI will fail otherwise).
- [ ] My commits follow the Conventional Commits format (e.g.,
`feat(themes): ...`, `fix(calculate): ...`).
- [ ] I have updated `README.md` if I added a new theme or URL
parameter.
- [ ] I have started the repo.
- [ ] I have made sure that i have only one commit to merge in this PR.
- [ ] The SVG output matches the CommitPulse "premium quality" aesthetic
standard (no raw elements, smooth animations, correct fonts).
- [ ] (Recommended) I joined the CommitPulse Discord community for
contributor discussions, mentorship, and faster PR support.

Author: JhaSourav07

app/components/CopyRepoButton.test.tsx

@@ -0,0 +1,109 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { render, screen, fireEvent, act } from '@testing-library/react';
+import CopyRepoButton, { REPO_URL } from './CopyRepoButton';
+
+describe('CopyRepoButton', () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    vi.useRealTimers();
+  });
+
+  // Test 1: Rendering and initial state
+  it('renders with default copy text', () => {
+    render(<CopyRepoButton />);
+    const button = screen.getByRole('button');
+    expect(button).toBeInTheDocument();
+    expect(button).toHaveTextContent('Copy URL');
+  });
+
+  // Test 2: Clipboard API is called with correct URL
+  it('copies repository URL to clipboard when clicked', async () => {
+    const writeText = vi.fn().mockResolvedValue(undefined);
+    Object.assign(navigator, {
+      clipboard: { writeText },
+    });
+
+    render(<CopyRepoButton />);
+    const button = screen.getByRole('button');
+
+    await act(async () => {
+      fireEvent.click(button);
+    });
+
+    expect(writeText).toHaveBeenCalledTimes(1);
+    expect(writeText).toHaveBeenCalledWith(REPO_URL);
+  });
+
+  // Test 3: Button label changes to 'Copied!'
+  it('changes button label to Copied! upon successful copy', async () => {
+    const writeText = vi.fn().mockResolvedValue(undefined);
+    Object.assign(navigator, {
+      clipboard: { writeText },
+    });
+
+    render(<CopyRepoButton />);
+    const button = screen.getByRole('button');
+
+    await act(async () => {
+      fireEvent.click(button);
+      // Wait for the promise to resolve and state to update
+      await Promise.resolve();
+    });
+
+    expect(button).toHaveTextContent('Copied!');
+  });
+
+  // Test 4: Button reverts after timeout
+  it('reverts to normal state after timeout duration', async () => {
+    const writeText = vi.fn().mockResolvedValue(undefined);
+    Object.assign(navigator, {
+      clipboard: { writeText },
+    });
+
+    render(<CopyRepoButton />);
+    const button = screen.getByRole('button');
+
+    await act(async () => {
+      fireEvent.click(button);
+      await Promise.resolve();
+    });
+
+    expect(button).toHaveTextContent('Copied!');
+
+    await act(async () => {
+      vi.advanceTimersByTime(2000);
+    });
+
+    expect(button).toHaveTextContent('Copy URL');
+  });
+
+  // Test 5: Handle clipboard failure
+  it('handles clipboard failure gracefully', async () => {
+    const consoleSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+    const writeText = vi.fn().mockRejectedValue(new Error('Clipboard permission denied'));
+    Object.assign(navigator, {
+      clipboard: { writeText },
+    });
+
+    render(<CopyRepoButton />);
+    const button = screen.getByRole('button');
+
+    await act(async () => {
+      fireEvent.click(button);
+      await Promise.resolve();
+    });
+
+    expect(button).toHaveTextContent('Copy failed');
+
+    await act(async () => {
+      vi.advanceTimersByTime(2000);
+    });
+
+    expect(button).toHaveTextContent('Copy URL');
+    consoleSpy.mockRestore();
+  });
+});