I had not added tests for because couldn't find a good place for adding new tests. It looks that there are no special tests for creating new type with type() at all. Proposed patch adds separate class with tests in test_builtin (may be this is not the best place, I'm not sure). They test type() with valid and invalid arguments, and also test setting some attributes, because error handling should be consistent for constructor and setters. There are some of setting tests in test_descr, but this doesn't look a good place for testing the constructor.
LGTM and I think test_builtins works well enough (unless you really wanted to go through the effort of consolidating all type-related types into a single test_type module).
I presume that there are existing tests that class statements work. Is so, these implicitly test type(name, bases, namespace). But I can see value to test testing the two phases of class creation separately. Test 'class' with a mock type that records the arguments passed, and separately test type explicitly.
