def METHOD_NAME(self):
    unused_prefix_index = 2
    test_namespace = "test namespace"
    node = self.__class__.MockNode({
        _prefix(1): "another namespace",
        _prefix(3): test_namespace,
        _prefix(4): "another namespace"})
    result = Typer.genprefix(node, ("unused-prefix", test_namespace))
    assert result == (_prefix(unused_prefix_index), test_namespace)
    expected_calls = [(_prefix(i), None)
        for i in range(1, unused_prefix_index + 1)]
    assert node.mock_call_params == expected_calls