public void GetOrCreateChapterAsyncShouldReturnChapterIfItExistsForTheCurrentPeriod()
{
//Arrange
var existingPeriod = new Period {
Id = _random.NextPositive()
};
var courseCode = Guid.NewGuid().ToString();
var existingChapter = new ChapterBuilder().WithId()
.WithCourse(courseCode)
.WithPeriod(existingPeriod).Build();
_periodRepositoryMock.Setup(repo => repo.GetCurrentPeriodAsync()).ReturnsAsync(existingPeriod);
_chapterRepositoryMock.Setup(repo => repo.GetSingleAsync(It.IsAny <string>(), It.IsAny <int>(), It.IsAny <int>()))
.ReturnsAsync(existingChapter);
//Act
var result = _service.GetOrCreateChapterAsync(courseCode, existingChapter.Number).Result;
//Assert
_periodRepositoryMock.Verify(repo => repo.GetCurrentPeriodAsync(), Times.Once);
_chapterRepositoryMock.Verify(repo => repo.GetSingleAsync(courseCode, existingChapter.Number, existingPeriod.Id), Times.Once);
_chapterRepositoryMock.Verify(repo => repo.AddAsync(It.IsAny <Chapter>()), Times.Never);
Assert.That(result, Is.EqualTo(existingChapter));
}