feat: implement mock for importLibrary

[usefulthink]

Implemented a mock for importLibrary that returns the correct collection of api-objects in their mocked versions.

closes #468

[douar]

Hi @usefulthink!

I'm using the loader.importLibrary from @googlemaps/js-api-loader:

Does the mock importLibrary allow us to simulate an error to trigger catch block?

Any information would be much appreciated, thank you!

[usefulthink]

In this case you should probably use jest.mock() to to mock out the actual implementation of the @googlemaps/js-api-loader module and replace the functions involved in the code you're testing. Then you can fully control what you want the loader to do in order to test how your application responds instead of testing with the api-loader in the loop which can be quite error-prone.

I've done something like that here, and it greatly simplified the whole testing setup: https://github.com/googlemaps/react-wrapper/blob/4667a308533f54591d89057775eb6ec8c4e73b35/src/index.test.tsx

[douar]

I will give that a try! Thank you!

[usefulthink]

@douar One more thing I just thought about - if you need the actual return values of importLibrary in your tests, you can do that as well. Here's an example for that: https://github.com/visgl/react-google-maps/blob/main/src/components/__tests__/info-window.test.tsx#L24-L36 (in that test, the useMapsLibraryMock is roughly equivalent to the Loader.importLibrary function).

[douar]

@douar One more thing I just thought about - if you need the actual return values of importLibrary in your tests, you can do that as well. Here's an example for that: https://github.com/visgl/react-google-maps/blob/main/src/components/__tests__/info-window.test.tsx#L24-L36 (in that test, the useMapsLibraryMock is roughly equivalent to the Loader.importLibrary function).

That is definitely helpful! Thank you for the references and resources 😄