Unit Test Refactoring: Possible standards for writing tests

Here are proposed standards required in all new unit tests:

• Each describe block should test only one function
• Each it block should test only one test case (contain only one call to the tested function)
• The describe block description should contain the name of the function being tested, and the class it belongs to (ie. “Tests for function USSNode.getChildren”)
• Each describe block should contain the following blocks:

jest.afterEach(() => { jest.clearAllMocks(); });
jest.afterAll(() => { jest.restoreAllMocks(); });

What do you guys think about these rules? Should their enforcement be automated? Changes? Thoughts?

[jellypuno]

I think @zFernand0 did great in re-factoring the Profiles Unit Testing. It is readable and understandable. After adding the Edit Profiles feature, it was easy for me to add new tests. 👍

[ghost]

Regarding the proposal to require these blocks:

jest.afterEach(() => { jest.clearAllMocks(); });
jest.afterAll(() => { jest.restoreAllMocks(); });

Additional changes must be made to our unit tests for the above code blocks to be effective. According to Jest docs:

Beware that jest.restoreAllMocks() only works when the mock was created with jest.spyOn; other mocks will require you to manually restore them.

Currently many of our mocks require manual restoring, because we manually create the mocks by overriding functions with jest.fn().

When our mocks are not restored, we experience problems like #710. (Tests fail to run with the --runInBand option, because test reporters like jest-stare are running in the same Node process as the unit tests, and trying to use the fs module which still has active mocks.)

If we want to make use of jest.restoreAllMocks(), we should consider creating our mocks with jest.spyOn instead of our current approach.