OpenMocks

OpenMocks is a lightweight utility library in the JavaScript and TypeScript testing ecosystem designed to simplify the creation, inspection, and lifecycle management of mocks and spies in unit tests. By centralizing mock control, it aims to improve test isolation and determinism, reducing the risk of state leakage between tests.

Typically, openMocks-style tooling is used alongside existing test runners such as Jest, Vitest, or Mocha. It provides mechanisms to create mock implementations for functions or modules, to record and inspect invocation data, and to restore original behavior when tests complete. The core concepts include mocks, spies, and stubs, with utilities to reset, clear, or close mocks in a predictable order.

Usage generally involves integrating the library with the test setup, opening mocks at the start of a test or suite, performing test actions against the mocked interfaces, and then closing or resetting mocks in a teardown phase. This lifecycle helps ensure that each test runs against a clean mock environment and that side effects do not persist.

Limitations include variability in API design across different openMocks implementations, potential overhead for large test suites, and the possibility that some projects may rely on framework-native mocking features rather than an external helper. As with any mocking tool, careful use is recommended to keep tests readable and maintainable.

See also: mocking in JavaScript, Jest, Vitest, Sinon, test doubles.