Improve builder tests

[yjaaidi]

1. There should be a calledTimes(1) here

   semver/packages/semver/src/builders/version/builder.spec.ts

   Line 156 in 2fdf2c3

   expect(fs.readFile).toHaveBeenLastCalledWith(

   but for some reason, this is called 6 times.
2. MockBuilderContext seems to read the filesystem for some reason. We should avoid that.
3. Shouldn't we automock fs etc... with jest.mock('fs')?

cc. @edbzn
Maybe this should be an issue 😅

[edbzn]

The number of call comes from the number of tests (6), it seems that the mock isn't cleared after each test, the following line fixe this :

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

But I don't really understand why the mock isn't automatically cleared after each test.

[yjaaidi]

Actually, it's because we are mocking fs.readFile manually. I think it's better to just restore this specific mock to be more explicit.