public void AddMovieToWishListShouldAddMovieToWishListMovies() { DbContextOptions <UltimateMoviesDbContext> options = new DbContextOptionsBuilder <UltimateMoviesDbContext>() .UseInMemoryDatabase(databaseName: "Users_AddMovieToWishList_Database") .Options; UltimateMoviesDbContext db = new UltimateMoviesDbContext(options); IUsersService usersService = new UsersService(db); db.Users.Add(new UMUser { UserName = "******" }); db.SaveChanges(); db.Movies.Add(new Movie { Name = "Test 1" }); db.SaveChanges(); usersService.AddMovieToWishList("Tester", db.Movies.Last().Id); int wishListMoviesCount = db.WishListMovies.Count(); Assert.Equal(1, wishListMoviesCount); }