feat: migrate testing framework to Bun and update test configurations

- Updated GitHub Actions workflow to use Bun's test runner and coverage reporting.
- Added comprehensive testing documentation for the Gitea Mirror project.
- Refactored test scripts in package.json to align with Bun's testing commands.
- Created new test files for database, Gitea, GitHub, health, and mirroring APIs.
- Implemented mock functions for API tests to handle various scenarios and responses.
- Established a test setup file for consistent test environment configuration.

docs/testing.md

@@ -0,0 +1,127 @@
+# Testing in Gitea Mirror
+
+This document provides guidance on testing in the Gitea Mirror project.
+
+## Current Status
+
+The project now uses Bun's built-in test runner, which is Jest-compatible and provides a fast, reliable testing experience. We've migrated away from Vitest due to compatibility issues with Bun.
+
+## Running Tests
+
+To run tests, use the following commands:
+
+```bash
+# Run all tests
+bun test
+
+# Run tests in watch mode (automatically re-run when files change)
+bun test --watch
+
+# Run tests with coverage reporting
+bun test --coverage
+```
+
+## Test File Naming Conventions
+
+Bun's test runner automatically discovers test files that match the following patterns:
+
+- `*.test.{js|jsx|ts|tsx}`
+- `*_test.{js|jsx|ts|tsx}`
+- `*.spec.{js|jsx|ts|tsx}`
+- `*_spec.{js|jsx|ts|tsx}`
+
+## Writing Tests
+
+The project uses Bun's test runner with a Jest-compatible API. Here's an example test:
+
+```typescript
+// example.test.ts
+import { describe, test, expect } from "bun:test";
+
+describe("Example Test", () => {
+  test("should pass", () => {
+    expect(true).toBe(true);
+  });
+});
+```
+
+### Testing React Components
+
+For testing React components, we use React Testing Library:
+
+```typescript
+// component.test.tsx
+import { describe, test, expect } from "bun:test";
+import { render, screen } from "@testing-library/react";
+import MyComponent from "../components/MyComponent";
+
+describe("MyComponent", () => {
+  test("renders correctly", () => {
+    render(<MyComponent />);
+    expect(screen.getByText("Hello World")).toBeInTheDocument();
+  });
+});
+```
+
+## Test Setup
+
+The test setup is defined in `src/tests/setup.bun.ts` and includes:
+
+- Automatic cleanup after each test
+- Setup for any global test environment needs
+
+## Mocking
+
+Bun's test runner provides built-in mocking capabilities:
+
+```typescript
+import { test, expect, mock } from "bun:test";
+
+// Create a mock function
+const mockFn = mock(() => "mocked value");
+
+test("mock function", () => {
+  const result = mockFn();
+  expect(result).toBe("mocked value");
+  expect(mockFn).toHaveBeenCalled();
+});
+
+// Mock a module
+mock.module("./some-module", () => {
+  return {
+    someFunction: () => "mocked module function"
+  };
+});
+```
+
+## CI Integration
+
+The CI workflow has been updated to use Bun's test runner. Tests are automatically run as part of the CI pipeline.
+
+## Test Coverage
+
+To generate test coverage reports, run:
+
+```bash
+bun test --coverage
+```
+
+This will generate a coverage report in the `coverage` directory.
+
+## Types of Tests
+
+The project includes several types of tests:
+
+1. **Unit Tests**: Testing individual functions and utilities
+2. **API Tests**: Testing API endpoints
+3. **Component Tests**: Testing React components
+4. **Integration Tests**: Testing how components work together
+
+## Future Improvements
+
+When expanding the test suite, consider:
+
+1. Adding more comprehensive API endpoint tests
+2. Increasing component test coverage
+3. Setting up end-to-end tests with a tool like Playwright
+4. Adding performance tests for critical paths