strong‑mock is a TypeScript‑first mocking library that lets you create fully type‑safe test doubles. By defining expectations up‑front with `when(...).thenReturn/thenResolve/thenThrow` and optional matchers, it enforces correct usage, provides detailed error diffs, and supports verification, reset, and promise handling—making it ideal for developers who want compile‑time safety and clear, deterministic mock behavior in unit tests.