My conversations with gullible machines...: January 2009

Update 2010-03-10: The following extension has now been superseded by the TestCase attribute which is now a part of the NUnit core (v2.5 and later). (nunit.framework.dll)

For an equivalent code sample, see the end of the post.

End of Update

This extension allows you an elegant way of handing the scenario where you need to run with different sets of input values. Usually tests shouldn't take any inputs... (the test runner doesn't know what inputs to supply the test with).


[Test(Description="PlainVanilla")]
public void TestBasicMath()
{
Assert.AreEqual(1, 1, "Someone broke mathematics");
}

But then there are always 'exceptions to the rule'. For example I'm writing a class called the Tokenizer that reads tokens from an input string. So I give it "10 + 15", the first token returned by the class should be the number 10.
Now I need to exercise the test code block below with different inputs for sInput like "10", " 10 + 15"


Tokenizer t = new Tokenizer(sInput);
Assert.AreEqual( 2, t.GetNextToken() );

Now back in the old days, you'd need to write a test case for each possible data value. Now with Andreas Schlapsi's RowTest Extension which is bundled with NUnit, things are much simpler.
Prerequisites:

Needs NUnit 2.4.7 or later. I 'm using NUnit 2.4.8 for .Net 2.0. Get it here as always
Add a reference to the nunit.framework.extensions assembly (in addition to the usual nunit.framework to your test project


using NUnit.Framework;
using NUnit.Framework.Extensions;

namespace TestDynCalc
{
[TestFixture]
public class TestTokenizer
{

  [RowTest]
  [Row("10 + 15")]
  [Row("10")]
  [Row(" 10 +15", TestName = "WhiteSpaceBeforeFirstNumber")]
  [Row("+10+15", Description = "Read number from +10+15", ExceptionMessage = "No number found at beginning of input stream!", ExpectedException = typeof(ArgumentException))]
  public void ReadNumberFromInputString(string sInput)
  {
      Tokenizer t = new Tokenizer(sInput);
      Assert.AreEqual( 2, t.GetNextToken() );
  }

  [Test(Description="PlainVanilla")]
  public void TestBasicMath()
  {
      Assert.AreEqual(1, 1, "Someone broke mathematics");
  }
}
}

Whoa! Let me step through all that. The using directives are self explanatory.

The RowTest attribute (instead of Test) over a NUnit test method allows you to parameterize the test method and gets the ball rolling.
Next for every unique set of inputs, you need to run this test with, you add a Row attribute and specify the inputs as constructor arguments. (The extension is vocal about any mismatch between number of test method parameters and the number of inputs you supply. )
The Row Test also has some named parameters

TestName : Lets you specify a descriptive name for the specific 'sub-test'. See how the last child node of the RowTest has a different name in the the attached GUI Screenshot below.
Description: This seems to be broken. It's a NUnit feature.. allowing you to tag a test with some comments that will show up when you bring up Properties for the test case. (Right click > Properties)
ExpectedException, ExceptionMessage: Ideally I'd like this as a different test case. However you have the option to mark a set-of-inputs to indicate that 'this should cause this type of Exception with the following message'. See last Row attribute.

This is how the NUnit GUI renders a RowTest. Quite nice. (Of course, You should choose better names for your tests :) Each Row attribute is rendered as sub-node of the test with the relevant name and all the input params specified in brackets (comma seperated in case of multiple params).

Update

Moving from RowTest to TestCase: There are no big changes with using the new 2.5 TestCase attribute. You don't need an explicit RowTest attribute. Replace each Row attribute with a TestCase attribute.
The Exception properties have been renamed (inline with the 2.5 ExpectedException revamp. So check the docs on ExpectedException if you can't get something to work).. but easy to figure out via Intellisense.
Another improvement is an explicit Result property, which as you can guess would be used to verify the output of your test case. Before TestCase, you had to pass in another parameter in the RowTest named expectedOutput and take care to use it only for Asserting at the end of the test.


       [TestCase("10 + 15")]
       [TestCase("10")]
       [TestCase(" 10 +15", TestName = "WhiteSpaceBeforeFirstNumber")]
       [TestCase("+10+15", Description = "Read number from +10+15", ExpectedMessage = "No number found at beginning of input stream!", ExpectedException = typeof(ArgumentException))]
       public void ReadNumberFromInputString(string sInput)
       {
           Tokenizer t = new Tokenizer(sInput);
           Assert.AreEqual(2, t.GetNextToken());
       }