DBusTestCase should have some convenience functions for asserting during testing

[Brendan Donegan]

Often when writing tests using dbusmock we want to assert that the method was called with particular arguments, or called a particular number of times, etc. There should be some convenience functions in DBusTestCase for doing this. An example:

assertCalledWith('mymethod', 'arg1', 'arg2'...)
assertCalledMultiple('mymethod', 10)

There are other possibilities, but these are just two I can think of.