Enable clearMocks, resetMocks, and restoreMocks by default

[JamieMagee]

Describe the proposed change(s).

Jest config allows you to specify 3 flags regarding mocks in increasing order of strictness:

1. clearMocks: true clears the call count and args of any mocks before each test.
2. resetMocks: true goes a step further, and also clears any mock implementations / return values defined before each test.
3. restoreMocks: true is the strictest and actually removes all mocks from all functions before each test.

The default, unfortunately, is not to do any of this, which means out-of-the-box Jest makes it very easy to write unit tests that unintentionally rely on test ordering.

I think the bare minimum should be to enable clearMocks in jest.config.ts (and remove any explicit jest.clearAllMocks() calls). Ideally I would also like to enable resetMocks (and remove any explicit jest.resetAllMocks() calls). I'd like to evaluate use of restoreMocks once resetMocks is reached.

See jestjs/jest#10242 for more context

[viceice]

I'm ok with 1 but don't like 2 and 3. 2 and 3 are onyl for lazy people whow don't want to think about test order and side effects.
2 and 3 can also cause another performance penality and makes tests even slower than they already are.

[JamieMagee]

I agree about the potential for performance penalties, but I think it's a trade-off between test correctness and performance. Already, enabling clearMocks, I see test failures due to tests unintentionally relying on setup from other tests.

[HonkingGoose]

Looks like PR #20402 fixes something about mocking as well:

Context

• jest.resetAllMocks() now resets spy's, so don't reset if nor required
• if a spy has no mock implementation, it calls the original