public void CreatingRating_UnderNormalConditions_AddsRatingToRatingList() { //arrange var originalCountOfRatings = _ratingList.Count; var ratingToCreate = new RatingDto() { InstructorId = 6, ClassId = 6, RatingId = 6, ClassRating = 6, Comment = "test comment 6", InstructorRating = 6 }; var mockRepo = Mock.Create <IRatingRepository>(); Mock.Arrange(() => mockRepo.Create(Arg.IsAny <Rating>())) .DoInstead(() => _ratingList.Add(ratingToCreate)) .OccursOnce(); _ratingService = new RatingService(mockRepo); //act _ratingService.Create(ratingToCreate); var actualCount = _ratingList.Count; //assert Mock.Assert(mockRepo); Assert.That(actualCount, Is.EqualTo(originalCountOfRatings + 1)); }