When @parameterizing a test case with complex numbers:

@pytest.mark.parametrize("amplitude", [32768j])
def test_something(amplitude):
    # [...]

...the test case is enumerated using opaque IDs:

$ pytest-3 -v test.py 
test.py::test_something[amplitude0] PASSED                                   [100%]

It would be preferrable to add "complex" into the (short) list of types that are automatically converted via str().

I'm chasing this one down myself and will attach a PR. Thanks!