pytest-coverage

name	pytest-coverage
description	Run pytest with coverage, identify uncovered lines, and iteratively add tests until 100% coverage is reached.

Goal

Ensure all lines of code in the backend are covered by tests.

Steps

1. Generate Coverage Report

For the entire backend:

cd backend
pytest --cov --cov-report=annotate:cov_annotate

For a specific module:

pytest --cov=app.services.credit_service --cov-report=annotate:cov_annotate

For specific tests:

pytest tests/test_credit_service.py --cov=app.services.credit_service --cov-report=annotate:cov_annotate

2. Read Annotated Output

• Open the cov_annotate/ directory.
• Each source file has a matching annotated file.
• Lines starting with ! are not covered by tests.
• Files with 100% coverage don't need attention.

3. Add Missing Tests

For each uncovered line:

• Understand what the line does in context.
• Write a focused test that exercises that branch/path.
• For async endpoints, use pytest-asyncio with async def test_....
• For DB-dependent tests, use isolated fixtures (never the production DB).

4. Iterate Until 100%

Keep running and improving until no ! lines remain:

pytest --cov --cov-report=annotate:cov_annotate

Tips for This Project

• Service-layer tests (e.g., test_credit_service.py) should mock external calls (fal_client, S3, etc.).
• Use pytest.mark.asyncio for async FastAPI endpoints.
• Edge cases to test: invalid input, 0-credit balance, expired sessions, S3 upload failure.

Source: github/awesome-copilot — pytest-coverage