Clean up Unit Tests Checking Exceptions

[JoshKeegan]

Unit Tests that check Exceptions are being thrown (and that it's correct type of Exception) are currently done with try...catch blocks and Assert.Fail() in a relevant place.

Switch to using the ExpectedException syntax throughout.

[JoshKeegan]

Note that ExpectedException support has been dropped in the latest version of NUnit. Whilst the unit testing framework currently being used in the Microsoft one, if ever cross-platform compatibility is wanted, then using ExpectedException could make it more difficult to port the unit tests to a different framework.