public void TestAdd()
{
// Arrange
var entity = new FakeModel {
FirstProperty = "fake4", SecondProperty = 4
};
var index = 0;
ReaderMock.Setup(reader => reader.ReadLine())
.Returns(() => file[index++]);
ReaderMock.SetupGet(reader => reader.EndOfStream)
.Returns(() => index >= file.Length ? true : false);
var expectedEntityToCsv = EntityToCSV(file.Count() + 1, entity.FirstProperty, entity.SecondProperty);
// Act
TestedDataLayer.Add(entity);
// Assert
WriterMock.Verify(writer => writer.WriteLine(expectedEntityToCsv), Times.Once);
}