'Tests parametrized with ids as non-strings (#1857).'

def test_parametrized_ids_invalid_type(self, testdir):

    testdir.makepyfile('\n                                                import    pytest\n\n                                                @pytest.mark.parametrize("x,    expected",    [(10,    20),    (40,    80)],    ids=(None,    2))\n                                                def    test_ids_numbers(x,expected):\n                                                                assert    x    *    2    ==    expected\n                                ')
    result = testdir.runpytest()
    result.stdout.fnmatch_lines(['*ids    must    be    list    of    strings,    found:    2    (type:    int)*'])
