Currently we only have toBe, toEqual and toBeNil. We should probably add more matchers such as:
Adding the toThrow will greatly simplify our own testing of matchers, so it would make sense to implement this one first.
Added a basic toThrow matcher for exceptions #3
The toThrow matcher can be extended to take an expected parameter.
Added toBeTrue and toBeFalse matchers. #3
Implement a more advanced toThrow. #3
Added new methods toThrowWithMessage and toThrowWithType which are
automatically called from toThrow based on the type of the expected
parameter. They could also be called explicitly.
Add associated specs as well.