NUnit: How to run a test class on multiple objects - better alternative than TestCaseSourceAttribute?

Question

I want to test all implementations of an interface with the same test class. I already know the TestCaseSourceAttribute, so I have set it up to load the object instances from the static testObjects array. This code works as I want:

[TestFixture]
public class MySerializerTests
{
    // IStreamSerializers loaded by the TestCaseSource attribute.
    static object[] testObjects = new object[]
    {
        new BinarySerializer(),
        new XmlSerializer(),
        new JsonSerializer()
    };

    [Test, TestCaseSource("testObjects")]
    public void Serialize_NullStreamArgument_ThrowsArgumentException(IStreamSerializer serializer)
    {
        Map map = new Map();
        Assert.Throws<ArgumentNullException>(() => serializer.Serialize(null, map));
    }
}

However, I have to use [TestCaseSource("testObjects")] on every method, which makes it rather tedious for the amount of methods I have. Is there a way of replacing the TextCaseSource attribute with an attribute that works on the whole test class? Maybe similar to the way a parameterized FestFixture works?

I'd like something similar to this, but where I can pass instances of my tested classes via the constructor of the test class:

[TestFixture(0)]
[TestFixture(1)]
[TestFixture(2)]
public class MySerializerTests
{
    // IStreamSerializers loaded by the TestCaseSource attribute.
    static object[] testObjects = new object[]
    {
        new BinarySerializer(),
        new XmlSerializer(),
        new JsonSerializer()
    };

    int currentIndex;

    public MySerializerTests(int index)
    {
        currentIndex = 0;
    }

    [Test]
    public void Serialize_NullStreamArgument_ThrowsArgumentException()
    {
        Map map = new Map();

        Assert.Throws<ArgumentNullException>(() => testObjects[currentIndex].Serialize(null, map));
    }
}

Can you clarify what you want? The instances are held in a static array, so they are shared among all methods that refer to that array. — Charlie, May 23 '16 at 00:29
I added a better explanation to the question. My first example already works the way I want, but I am looking for a way to avoid having to use the TestCaseSource attribute on every method. Instead I would like to elegantly create all needed instances via a parameterized TestFixture or a similar way. It works perfectly fine with value types, but I can't pass a constructor call as a parameter. — Xarbrough, May 23 '16 at 11:36

score 3 · Accepted Answer · answered May 24 '16 at 18:23

You want the TestFixtureSourceAttribute.

[TestFixtureSource("testObjects")]
public class MySerializerTests
{
    // IStreamSerializers loaded by the TestCaseSource attribute.
    static IStreamSerializer[] testObjects = new IStreamSerializer[]
    {
        new BinarySerializer(),
        new XmlSerializer(),
        new JsonSerializer()
    };

    IStreamSerializer _serializer;

    public MySerializerTests(IStreamSerializer serializer)
    {
        _serializer = serializer;
    }

    [Test]
    public void Serialize_NullStreamArgument_ThrowsArgumentException()
    {
        Map map = new Map();
        Assert.Throws<ArgumentNullException>(
            () => _serializer.Serialize(null, map));
    }
}

I haven't compiled this, so you may need to fix typos, etc.

After checking the documentation, this looks like the perfect answer. Too bad that I'm using NUnit in Unity, which currently doesn't support the TestFixtureSource attribute; but that's a different problem, so I accept this as the answer and will look if I can update my framework version. — Xarbrough, May 24 '16 at 21:04

NUnit: How to run a test class on multiple objects - better alternative than TestCaseSourceAttribute?

1 Answers1