test-gen

Generate unit and integration tests for a given file or function.

Instructions

1. Read the target file the user specifies (or the most recently edited file if none given).

2. Identify the language and detect the existing test framework:

   • Python: pytest (check for conftest.py, pytest.ini, pyproject.toml)
   • TypeScript: Jest or Vitest (check package.json for jest or vitest)
   • Go: stdlib testing package
   • Rust: stdlib #[cfg(test)] module

3. Identify all public functions/methods and their behavior:

   • What inputs do they accept?
   • What outputs do they produce?
   • What side effects do they have (DB, HTTP, file I/O)?
   • What error conditions exist?

4. Generate tests following the unit-testing skill patterns:

   • AAA pattern (Arrange / Act / Assert)
   • Naming: test_<unit>_<scenario>_<expected> (Python), describe/it (TS), TestXxx (Go)
   • Edge cases: null/None/nil, empty collections, boundary values
   • Error paths: invalid input, missing dependencies, timeout
   • Parameterized tests where multiple input/output pairs test the same logic

5. For functions with external dependencies (DB, HTTP, filesystem):

   • Generate integration test stubs using Testcontainers or test clients
   • Mock external I/O with appropriate library (unittest.mock, jest.fn(), interface-based in Go)

6. Place the test file in the correct location:

   • Python: tests/test_<module>.py
   • TypeScript: <module>.test.ts (co-located) or __tests__/<module>.test.ts
   • Go: <module>_test.go (same package)
   • Rust: #[cfg(test)] mod tests at bottom of same file, or tests/ for integration

7. Run the tests to verify they pass. Fix any failures.

Output

• The generated test file
• A summary of what was tested and what was deliberately excluded (with reasoning)