C# – NUnit TestCaseSource

cnunittestcasesource

I'm having a go with the TestCaseSource attribute. One problem: when the sourceName string is invalid, the test just gets ignored instead of failing. This would be really bad if the source method gets renamed, the sourceName string doesn't get updated, and then you lose the coverage that the test provided. Is there a way to change the behaviour of NUnit, so that the test fails if the sourceName is invalid?

Best Answer

This is resolved in NUnit 2.6.2. There is a new constructor for the attribute that takes a Type (which must implement IEnumerable); it "is recommended for use in preference to other forms because it doesn't use a string to specify the data source and is therefore more easily refactored." (From the documentation.)

This does require that your test runner supports the latest NUnit.

A very basic example (see the above documentation link for more details):

public class TestDataProvider : IEnumerable
{
    public IEnumerator GetEnumerator()
    {
        return new List<int>{ 2, 4, 6 }.GetEnumerator();
    }
}

[TestFixture]
public class MyTests
{
    [TestCaseSource(typeof(TestDataProvider))]
    public void TestOne(int number)
    {
        Assert.That(number % 2, Is.EqualTo(0));
    }
}

Related Solutions

C# – Convert string to C# code

Creating attributes for your method on the fly is possible but hard. You're better off finding another approach.

Attributes (e.g. [TestFixture]) of the kind you have are read by the compiler when your code is compiled and inserted in to your code automatically.

To generate your own attributes for classes you'll need to use something like Reflection.Emit to modify generated assemblies as a post-build step for the project. This is like writing assembly language directly (you'd be creating MSIL) which might be fun but is not easy and would make your code very hard to maintain!

An alternative approach might be to have an enum control the test cases, and have a method that checks the enum and returns the appropriate data:

public enum TestController
{
    Value1,
    Value2,
    Value3
}

[TestFixture(TestController.Value1)]   
[TestFixture(TestController.Value2)]   
[TestFixture(TestController.Value3)]   
public class MyTestFixture   
{   
    public MyTestFixture(TestController testController)   
    {   
        var dataForTest = GetDataForTest(testController);
    }   

    ...   

}

The method GetDataForTest() would then have some kind of switch statement to generate the data.

An alternative approach might be to use a type rather than an enum, then instantiate the type in the GetDataForTest() method and call a factory method - but I think that might be a bit overcomplicated.

Best Answer

Related Solutions

C# – Convert string to C# code

Related Topic