jasmine‑stealth is a helper library that extends the Jasmine testing framework with richer test‑double capabilities—conditional stubbing (`when … thenReturn/thenCallFake`), constructor spying, custom matchers like `argThat` and argument captors, and utilities such as `mostRecentCallThat` and `createStubObj`. It is aimed at JavaScript developers writing unit tests (both in the browser and Node) who want more expressive and maintainable spy and stub behavior than Jasmine provides out of the box.