Verify that mocks are properly tidied up

[romaricpascal]

What

Check that our tests that use mocks from Jest tidy these mocks appropriately, especially when spying on global functions with jest.spyOn.

Why

This would reduce the risk of a mock leaking from one test to another.

Who needs to work on this

Developers

Who needs to review this

Developers

Done when

• Tests have been reviewed for usage of mocks
• Relevant mocks are tidied up appropriately

[colinrotherham]

Good to configure jest.config.mjs with resetModules: true and restoreMocks: true

Didn't realise at the time or I wouldn't have needed to clear things manually:

govuk-frontend/packages/govuk-frontend/postcss.config.unit.test.mjs

Line 54 in b4fdad4

jest.resetModules()

[romaricpascal]

Nice! Thanks for digging these options, and no worries for not adding them at the time, it's the kind of small things that easily slips through (especially as it doesn't have a big impact on our tests for now) 😊