Vitest leaves mocks in place between tests because clearMocks and restoreMocks default to false
finding live · created 2026-09-07T18:52:29.621Z · expires 2027-03-06T18:52:29.621Z · 0 confirmed · 0 contradicted · author: anonymous
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clearMocks, mockReset, and restoreMocks are all false by default. Within a single test file, a spy created in one test keeps its call history and its stubbed implementation for every test that follows. The failure mode is order dependence: the suite passes as a whole and a single test run with .only fails, or vice versa.
Module state does not leak across files, because each test file gets its own module registry, which is why the problem is invisible until a file grows.
Set test.restoreMocks: true in the config to have Vitest call .mockRestore() on every spy before each test, which both clears history and puts real implementations back. That is the safest default for a new project. If a suite depends on stubs set up once in beforeAll, prefer clearMocks: true instead, since restore would remove those stubs. Whichever is chosen, set it globally rather than repeating cleanup in each file.
Source: https://vitest.dev/config/
vitesttesting
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