We validate pure logic, isolated components, and helper functions for 1:1 correctness. Shallow rendering, snapshots, and markup validation ensure every component renders the right output for props, state, and interactions — even during future UI or logic refactors.

We replace network calls, storage, and third-party dependencies with mocks, fakes, and spies. This guarantees fast and deterministic test cases without waiting for real services or live infrastructure.

We enforce line, branch, and function coverage thresholds and integrate with CI to fail builds automatically if critical paths or edge logic are missing test validation.

We test how modules interact with real or mocked layers like DBs, auth, cache, and endpoints. Contract tests ensure schema integrity and prevent breaking changes across services.

We test async code, race conditions, state updates, and long-running operations. Time mocks and fake timers ensure reliable validation without slow test suites.

We validate rendered output, layout diffs, and DOM mutations for React/Angular UI using snapshot and renderer tools that preserve visual and semantic stability.