public async Task DeleteAsync_ValidCall()
        {
            await HomeworkService.DeleteAsync(It.IsAny <int>());

            RepositoryMock.Verify(m => m.Delete(It.IsAny <Homework>()));
            StudentHomeworkUpdaterMock.Verify(s => s.UpdateAsync(It.IsAny <Homework>(),
                                                                 StudentHomeworkUpdater.UpdateType.RemoveHomework, It.IsAny <bool>()));
        }
        public void DeleteAsync_ThrowsValidationException()
        {
            RepositoryMock.Setup(repo => repo.GetAsync(It.IsAny <int>()))
            .Returns(GetExceptionTest());

            Assert.ThrowsAsync <ValidationException>(async() => await HomeworkService.DeleteAsync(null));
            Assert.ThrowsAsync <ValidationException>(async() => await HomeworkService
                                                     .DeleteAsync(It.IsAny <int>()));
        }