Adventures in Testing – 2 – Row Attributes

Often, when writing Unit Tests you find yourself writing a batch of quite similar tests that exercise the various test cases for a method.

As I am endeavoring to add Unit Tests to all new code I write, I am learning my way through the MbUnit/Gallio Testing Framework which we have standardized on for all DNN testing.  MbUnit is an awesome testing framework and it has a number of Attributes that you can apply to a Test that allows you to provide different parameters. 

Listing 1 shows an example of using the Row attribute to provide three different sets of test data, rather than writing three separate tests.

   1:  [Test]

   2:  [Row("NoRecords", 0)]

   3:  [Row("OneIndividual", 1)]

   4:  [Row("TwoIndividuals", 2)]

   5:  public void ReadIndividual_Returns_The_Correct_No_Of_Records(string fileName, int recordCount)

   6:  {

   7:      //Arrange

   8:      GEDCOMReader reader;

   9:      GEDCOMRecordList records;

  10:   

  11:      //Act

  12:      using (Stream s = Util.GetTestFileStream(String.Format("GEDCOMReaderTests.{0}.ged", fileName)))

  13:      {

  14:          reader = GEDCOMReader.Create(s);

  15:          records = reader.ReadIndividuals();

  16:      }

  17:   

  18:      //Assert

  19:      Assert.AreEqual(recordCount, records.Count);

  20:  }

If you look at the method signature you will notice that there are two parameters, and there are also two parameters to the Row Attribute.  In this case I am writing a parser to read GEDCOM data (GEDCOM is a Genealogical Data Standard). 

The fileName parameter tells the test which GEDCOM file to use (line 12), and the recordCount parameter tells the test the number of records that the file should contain which is used in the Assert (line 19).  In this example (which is quite trivial) I am testing that files with 0, 1 and 2 records parse correctly. 

When the test is executed, all three sets of data are used – so we actually have 3 tests, and we get three results.

As more edge cases are determined – for example in this example we would probably want to test that the correct number of individuals are returned when the file contains other records as well (the GEDCOM standard supports a number of record types – families, notes, sources) – we can add extra tests by just adding Row attributes that correspond to the file names and expected record counts.