public void Should_Open_Reader_When_Mode_Is_Read() { //Arrange _csvReader = Substitute.For <ICSVReader>(); _csvWriter = Substitute.For <ICSVWriter>(); _csvReaderWriter = new CSVReaderWriter(_csvReader, _csvWriter); //Act _csvReaderWriter.Open(FilePath, CSVReaderWriter.Mode.Read); //Assert _csvReader.Received().Open(FilePath); _csvWriter.DidNotReceive().Open(FilePath); }