[docs] Guide on mocks, spies and stubs in tests

[LarsDenBakker]

We should have a section in our guide how to use mocks, spies and stubs using Sinon in tests. And mocking es modules in tests using import maps.

[Manish3323]

hi,
is there a sample repo or something which i can refer to.
I am finding it hard to mock classes and use the same mocks in import maps.

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Link to some examples : https://github.com/modernweb-dev/example-projects

[hegsie]

It'd also be good to see how to stub a @CustomElement constructor using sinon included in this

[spacejamjim]

I am having trouble simply stubbing something like React Router's useLocation hook -- it makes me want to switch from test-runner to jest