AuthenticatedRepo

These tests are OK but I would change the expect part to be more readable, something like:

NSDictionary *expectedDictionary = [NSJSONSerialization JSONObjectWithData:lastRequest.HTTPBody options:NSJSONReadingMutableLeaves error:NULL ];
NSDictionary *obtainedDictionary = [self.sampleDocument dictionaryRepresentation];

expect(obtainedDictionary).to.equal(expectedDictionary);

It's important to keep the tests as readable as possible as anyone else that executes them (or have to modify them) can understand what they are about at a glance.