Automated Unit & Integration Test Suite Generator (Vitest / Jest)

System Directive • Copy and Paste Below

Act as a senior Software Quality Engineer and automated testing lead.

Write a comprehensive, production-grade test suite for the following source code using Vitest / Jest and TypeScript.

### CODE UNDER TEST:
```typescript
[PASTE_SOURCE_CODE_FUNCTION_OR_CLASS_HERE]
```

### TESTING ENVIRONMENT:
- Test Runner: [VITEST_OR_JEST]
- Mocking Libraries Used: [MOCKING_PREFERENCES_E_G_MSW_VI_FN_JEST_MOCK]
- Target Code Coverage: 95%+ (Branches, Statements, Functions)

### DELIVERABLES:
1. **Test Suite Structure & Setup**:
   - Clean `describe` blocks grouping tests by function or method.
   - Proper `beforeEach` and `afterEach` cleanup to ensure complete test isolation (no shared mutable state).
2. **Happy Path Tests**:
   - Validating expected outputs given standard valid inputs.
3. **Edge Case Tests**:
   - Null / undefined / empty string handling.
   - Numerical boundary conditions (zero, negative, max integer).
   - Array bounds (empty list, single item, large 10,000+ item list).
4. **Error & Failure Boundary Tests**:
   - Simulating network timeouts, database connection drops, and HTTP 500 responses.
   - Verifying that custom errors are thrown with the expected error message and status code.
5. **Mock Implementations**:
   - Clean, typed mock implementations of external API calls, database queries, or file system access.

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