If I want to mock a class that returns a string that is used to determine whether while loop should continue (imagine read while string != null), how can I set the expectation. I have tried the following:
provider.Reader.Expect(r => r.ReadLine()).Return("1,10,20");
provider.Reader.Expect(r => r.ReadLine()).Return(null);
but when it is called twice in the same method, it returns the first string on both occasions, whereas I want it to return the second value (null) if called a second time.