对该单元进行单元测试还是不进行单元测试

Question

I have a CSV class and a CSV parser class, and their unit tests. I want to find out if part of the unit test below must be removed:

public class CSV{

public string[] columns GetColumns()
        {                       
           var columns = null;

            if (!string.IsNullOrEmpty(this.textReader.ReadLine()))
            {
               var columns = this.csvParser.GetColumns(line);              
            }

            return columns;
        }



  }

   [Test]
        public void GetColumns_ReturnsCorrectLine()
        {            
            reader.Setup(r => r.ReadLine()).Returns("a\tb\tc");


            //Act
            var columns = csvReader.GetColumns();

            //Assert
            Assert.IsTrue(columns!=null);
            Assert.AreEqual(3, columns.Length);

            Assert.AreEqual("a", columns[0]);
            Assert.AreEqual("b", columns[1]);
            Assert.AreEqual("c", columns[2]);
      }

Question

1) Must the three lines of code that assert columns (a,b,c) be removed?

2) Does the GetColumns_ReturnsCorrectLine test method perform correct unit test after removing the last three assertions

Please note that there are already code that unit tests the CSV parser's GetColumns() method. The functionality of GetColumns is to parse a tab-delimietered string and turn it into columns.

Any idea?

Answer 1

Those values should be checked but not like you are doing.

With NUnit, there is CollectionAssert :

CollectionAssert.AreEqual(new [] {"a", "b", "c"}, columns);

Answer 2

Must the three lines of code that assert columns (a,b,c) be removed?

tl;dr: No

If you want to make sure that "a\\tb\\tc" results in ["a", "b", "c"] and not ["b", "a", "c"], then you should leave them in. The first two lines only check if it's not null and the length, content could be anything.

Please note that there are already code that unit tests the CSV parser's GetColumns() method.

What are those tests? It's hard to tell if they overlap without seeing them.

Answer 3

It looks as if you are trying to test the CSV.GetColumns().

GetColumns() has three paths

1) textReader.ReadLine() returns null => return null
2) textReader.ReadLine() returns "" => return null
3) testReader.ReadLine() returns !string.NullOrEmpty() => return the output from the CsvParser.

Three tests should be that

TextReader returns null => result is null
TextReader returns "" => result is null
TestReader returns => result is return value of CsvParser.

The values returned by the CsvParser are not important - as you mention, that the CsvParser does its job properly is tested elsewhere - we just want to say that we return the output of the parser.

public interface ITextReader {
    string ReadLine();
}

public interface ICsvParser {
    string[] GetColumns(string line);
}

public class CSV {
    private readonly ITextReader textReader;
    private readonly ICsvParser csvParser;

    public CSV(ITextReader textReader, ICsvParser csvParser) {
         this.textReader = textReader;
         this.csvParser = csvParser;
    }

    public string[] GetColumns() {                       
        string[] columns = null;
        var line = this.textReader.ReadLine();          

        if (!string.IsNullOrEmpty(line)){
           columns = this.csvParser.GetColumns(line);              
        }

        return columns;
    }

}

[TestClass]
public class CSVFixture {
    private Mock<ITextReader> mockTextReader;
    private Mock<ICsvParser> mockCsvParser;
    private CSV csv;

    private readonly static string [] Columns = new string[]{};

    [TestInitialize]
    public void Setup() {
        mockTextReader = new Mock<ITextReader>();
        mockCsvParser = new Mock<ICsvParser>();
        csv = new CSV(mockTextReader.Object, mockCsvParser.Object);
    }


    [TestMethod]
    public void NullLine() {
        Execute(null);
    }

    [TestMethod]
    public void EmptyLine() {
        Execute("");
    }

    [TestMethod]
    public void PopulatedLine() {
        Execute("SomeLineValue", Columns);
    }

    private void Execute(string line, string[] expected = null) {
        mockTextReader.Setup(mk => mk.ReadLine()).Returns(line);
        mockCsvParser.Setup(mk => mk.GetColumns(line)).Returns(Columns);

        var actual = csv.GetColumns();

        Assert.AreEqual(actual, expected);

    }
}

Other Points: As long as the CsvParser is only invoked from here it is only moving code around but you might change the CsvParser so that if the input is null or empty it returns null. This means that you do not have to check for it every time you invoke the CsvParser.