Refactoring 05: Testing and Regression

Goal

Protect core logic with small, fast tests and regression checks for key metrics.

Sequence

• Order: 05
• Previous: refactoring-04-data-io-validation
• Next: refactoring-06-static-analysis-style

Workflow

• Identify stable, critical functions and write unit tests first.

- Success: Core logic has focused unit tests.

• Add regression tests for metrics or outputs using small fixtures.

- Success: Key metrics have stable regression checks.

• Keep tests fast; mark slow or data heavy tests as optional.

- Success: Default test run finishes quickly.

• Prefer deterministic fixtures over sampling from large datasets.

- Success: Tests run deterministically without external data.

• Add a single command to run tests via uv run.

- Success: One documented command runs the full test suite.

Guardrails

• Avoid testing training loops end to end unless requested.
• Do not add flaky tests; stabilize randomness before asserting values.
• Keep test data small and stored under tests/.