tests: branches coverage in test_authentication, test_background, test_responses, test_routing

[lealre]

Summary

Related to issue #2452

This PR addresses the cases in the test files below and essentially adds #pragma: no branch to all the cases, except for test_authentication, where I changed the #pragma: no cover line to cover the function that is not used.

From what I can see, there are no branch options to be covered, as the code relies on elif conditions or depends on a condition to pass the test.

File	Branches
tests/test_authentication.py	213->210
tests/test_background.py	76->exit
tests/test_responses.py	268->exit, 752->exit
tests/test_routing.py	800->802, 874->exit

The only one I don't fully understand is test_routing (line 874), where it's marking the @pytest.parametrized test as having uncovered branches.

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.