public void TestExceptionThrownByAverageGradeOfMovie(int movieId)
        {
            List <Movie> movies = new List <Movie>()
            {
                new Movie {
                    Reviewer = 1, Grade = 1, MovieId = 1
                },
                new Movie {
                    Reviewer = 1, Grade = 1, MovieId = 2
                },
                new Movie {
                    Reviewer = 2, Grade = 2, MovieId = 3
                },
                new Movie {
                    Reviewer = 2, Grade = 3, MovieId = 3
                },
                new Movie {
                    Reviewer = 3, Grade = 4, MovieId = 2
                }
            };
            MovieSystem ms = new MovieSystem(movies);

            Assert.Throws <InvalidDataException>(() => ms.AverageGradeOfMovie(movieId));
        }
        public void TestAverageGradeOfMovie(double expRate, int movieId)
        {
            List <Movie> movies = new List <Movie>()
            {
                new Movie {
                    Reviewer = 1, Grade = 1, MovieId = 1
                },
                new Movie {
                    Reviewer = 1, Grade = 2, MovieId = 2
                },
                new Movie {
                    Reviewer = 2, Grade = 3, MovieId = 3
                },
                new Movie {
                    Reviewer = 2, Grade = 3, MovieId = 3
                },
                new Movie {
                    Reviewer = 3, Grade = 2, MovieId = 2
                }
            };
            MovieSystem ms = new MovieSystem(movies);

            Assert.Equal(expRate, ms.AverageGradeOfMovie(movieId));
        }