essential-test-design

What problem does it solve?

Tests that are tightly coupled to implementation details create false positives and false negatives, undermining their ability to detect real regressions. This Skill helps authors and reviewers shift focus from internal mechanics to the observable contract so tests remain valuable across refactors.

Core Features & Use Cases

• Behavior-first guidance: Emphasizes asserting observable outcomes and boundary conditions rather than spying on internal calls.
• Decision framework: A short checklist to define the contract, the regression to catch, and whether a test would survive internal refactoring.
• Common scenarios: Practical patterns for async delays, debounce/throttle logic, data transformation, side effects (API/DB), and retry logic, with recommendations for fakes, mocks at boundaries, and boundary assertions.
• Reviewer aid: Use during test reviews to identify brittle assertions and convert them into robust contract tests.

Quick Start

Ask the assistant to review a failing or flaky test and rewrite assertions so they verify the observable behavior boundary rather than implementation details.