Testing Best Practices

What it does

This skill provides a comprehensive guide to testing best practices, focusing on unit and integration testing using TypeScript with Jest/Vitest. It offers 34 rules across seven categories designed to help developers write reliable, maintainable test suites. The skill assists in improving code quality by providing guidelines for structuring tests, ensuring isolation, crafting assertions, managing test data, utilizing mocking effectively, achieving meaningful coverage, and optimizing performance.

When to use it

• When writing new unit or integration tests.
• During code reviews to assess the quality of existing test code.
• To improve overall test coverage strategy.
• When setting up a testing infrastructure.
• For debugging flaky or slow tests.
• To ensure tests run independently and reliably.

Key capabilities

• Rule-Based Guidance: Provides 34 specific rules categorized by priority (Critical, High, Medium, Low).
• Test Structure Best Practices: Covers principles like the Arrange, Act, Assert (AAA) pattern, descriptive test names, and proper setup/teardown.
• Isolation Focus: Emphasizes independent tests with no shared state and deterministic results.
• Assertion Guidelines: Promotes specific assertions, meaningful error messages, and avoiding "magic numbers."
• Test Data Management: Includes techniques like factories, builders, and using realistic fake data.
• Mocking Strategies: Offers guidance on strategic mocking and verifying interactions.
• Coverage Optimization: Focuses on achieving meaningful coverage of edge cases and error scenarios rather than striving for 100% coverage.

Example prompts

• "Show me the rules related to test structure."
• "What are some best practices for isolating my tests?"
• "Give me an example of how to use a data factory in my testing workflow."
• “How can I improve the performance of my unit tests?”

Tips & gotchas

• The skill is primarily geared towards TypeScript projects using Jest/Vitest.
• Focus on understanding and applying the "Critical" priority rules first, as these have the most significant impact on test reliability.
• Remember that 100% code coverage isn't always a worthwhile goal; focus on covering meaningful scenarios and edge cases instead.