Support toContain with element.classList

[vekunz]

Clear and concise description of the problem

We are building a lot of components and want to test as many features as possible. One of the things we often have to test is if classes are attached correctly to an HTMLElement. Currently, we use this approach:

expect(element.classList.contains('something')).toBeTruthy();

This works but does not give us a good error message if the expectation fails. In this case, we just get the message that it is not true but false (except we add an error message manually).

Suggested solution

It would be great if we could use .toContain for this purpose. It would have the benefit of meaningful error messages if the expectation fails (e.g. a list of the actual classes of the element).

expect(element.classList).toContain('something');

Alternative

No response

Additional context

No response

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