This test method is doing way too much work.  Split it into these smaller methods:

1) `test_parse_answer_error()`
2) `test_interpret_error()`
3) `test_staff_answer_error()`
4) `test_radio_grades()`
5) `test_checkbox_grades()`

You should also move constants used by the test into class variables, which are by conventional capitalized: for example, `TEST_PROBLEMS`