Test conditional import code

[anatoli26]

In my package I'm checking for an extra dependency with a code like this:

try:
    import typer
except ImportError:
    print("error: typer not installed", file=sys.stderr)
    sys.exit(1)

Can't find a way to test this. Patching "builtins.__import__" with a temporary mock_import works only if no previous import typer calls were made.

So if invoking pytest test_dynamic_import.py, it's working, but bare pytest analyzes and performs imports in other testfiles that import the main package where the dynamic import code is executed, so typer is already imported when the test function with the patch code in the test_dynamic_import.py file is invoked.

I believe there should be a more straightforward method to test for dynamic imports. Please, advise.