Improve integrations tests

[MichalKalita]

How tests can look:

1. Correctness—We must be sure what we're testing and what the result is, and that we really test it, and only one single output is correct.
2. Minimal complexity - ideally just input/output. Or just input/update/output.
3. Exact results - for example, expect(toolNames).toEqual(["a", "b", "c"]) tells me that tools a, b, c are there
4. Documentation - some projects use tests to document how the library can be used. This only works when it's input/output testing with no additional logic, so the code can be easily read.

I will look for some better materials on how to write integration tests.