public async Task AddRangeAsync_Test()
        {
            var options = new DbContextOptionsBuilder <ApplicationContext>()
                          .UseInMemoryDatabase(databaseName: "AddTestDatabase")
                          .Options;

            using (var context = new ApplicationContext(options))
            {
                context.Database.EnsureCreated();
                var repository = new CourseRepository(context);
                var newCourses = new List <Course>
                {
                    new Course
                    {
                        Name       = "New",
                        LecturerId = 1
                    },
                    new Course
                    {
                        Name       = "New",
                        LecturerId = 2
                    }
                };
                var prevCount = repository.GetAll().Count();
                await repository.AddRangeAsync(newCourses);

                await context.SaveChangesAsync();

                var courses = repository.GetAll();
                Assert.That(courses.Count(), Is.EqualTo(prevCount + 2));
            }
        }