'Report that the given test failed, and was expected to do so.
In Trial, tests can be marked \'todo\'. That is, they are expected to
fail.
@type test: L{pyunit.TestCase}
@type error: L{Failure}
@type todo: L{unittest.Todo}, or L{None}, in which case a default todo
message is provided.'

def addExpectedFailure(self, test, error, todo=None):

    if (todo is None):
        todo = makeTodo(self._DEFAULT_TODO)
    self.expectedFailures.append((test, error, todo))
