TestCases with multiple parts of the same type will ignore the second part

[David Coles]

If you create a TestCase with two test case parts that both test the same type of test one will get ignored. This is due to a design decision of TestFramework that means only one test of each type can be assigned.

How to reproduce:
Create a new Exercise which contains a Test Case with two Test Case Parts using a comparator function on stdout. Have one return True and one return False. Note that when you run this Exercise the Exercise will still pass despite one of the Test Case Parts reporting failure.

Solution is to rewrite TestFramework in such a way that it can handle multiple instances of the same test case part.