Here is a modification of test_unit_tx.py that still pass, but should not (I added an `assert False`): ```python # compute_amounts() def test_compute_amounts_errors(capsys): trials = (((0.0031, 1), 314),) for trial in trials: # check program exit on error with pytest.raises(SystemExit) as pytest_exit: # read output to check error. tx.compute_amounts( trial[0], trial[1], ) expected_error = "Error: amount {0} is too low.".format(trial[0][0]) assert capsys.readouterr() == expected_error # Assert False to show there is a bug in this kind of context assert False assert pytest_exit.type == SystemExit ``` It means that basically, all assertions in a context like `with pytest.raises(SystemExit) as pytest_exit:` are not tested if ther is a `message_exit()`, because the function exits first. I don't know how to solve it for now.