tdd

name	tdd
description	Commands, step-by-step procedures, and mechanical execution for test engineering, testability audits, and the TDD lifecycle. You MUST load this skill when executing test tasks, designing tests, doing TDD, or verifying system behavior.
license	MIT

Test-Driven Development (TDD) & Test Engineering Execution

Skill Focus: Commands, step-by-step procedures, and mechanical execution for test engineering, testability audits, and the TDD lifecycle.

WHEN TO USE

• When executing test tasks, designing tests, or verifying system behavior.
• When requested to write tests or practice Test-Driven Development (TDD).
• When conducting testability audits on existing or new codebases.
• When addressing bugs that require regression test coverage.

WHEN NOT TO USE

• Rapid prototyping or throwaway exploratory code where architecture is highly fluid.
• Pure configuration file updates or minor static text changes without logic.
• UI/CSS styling tweaks that are verified visually rather than behaviorally.

Common Pitfalls

• Testing Implementation Details: Coupling tests to private methods or specific internal structures, making refactoring impossible without breaking tests.
• Over-Mocking: Mocking everything to the point where the test only verifies that mocks were called, not that the system behaves correctly.
• Skipping the Refactor Step: Writing passing tests but leaving the implementation messy and unoptimized, leading to technical debt.
• Testing Too Much at Once: Trying to test multiple behaviors or edge cases in a single test block, making failures hard to diagnose.