Writing Quality Tests

Overview

High-signal tests prove behavior, not implementation. While TDD focuses on the process of writing tests first, this skill focuses on the artifact—making tests stable, explicit, and valuable long-term.

Core rule: If a test is nondeterministic or tied to internals, it is debt. Fix it.

When to Use

• New features: "I need to add tests for this new API endpoint/component."
• Bug fixes: "Help me write a regression test for this bug before fixing it."
• Flaky tests: "This test fails randomly on CI. How do I make it deterministic?"
• Refactoring: "I want to refactor this legacy code but the tests are brittle. How do I improve them first?"
• Slow tests: "The test suite takes too long. How can I speed it up or mock dependencies effectively?"
• Test Design: "Should I use a unit test or integration test for this logic?"
• Review: "Check these tests for maintainability, coverage, and clarity."
• Not for manual exploratory testing or load/perf-only work.