### TestFixtureAttribute (NUnit 2.0 / 2.5)

This is the attribute that marks a class that contains tests and, optionally, setup or teardown methods. NUnit 2.5 introduces parameterized and generic test fixtures - see below.

There are a few restrictions on a class that is used as a test fixture.

- It must be a publicly exported type.
- It must have not be abstract.
- A non-parameterized fixture must have a default constructor.
- A parameterized fixture must have a constructor that matches the parameters provided.

If any of these restrictions are violated, the class is not runnable as a test and will display as an error in the Gui.

In addition, it is advisable that the constructor not have any side effects, since NUnit may construct the object multiple times in the course of a session.

Beginning with NUnit 2.5, the TestFixture attribute is optional for non-paramterized, non-generic fixtures, so long as the class contains at least one method marked with the Test, TestCase or TestCaseSource attribute.

#### Example:

C#
VB
C++
J#

    namespace NUnit.Tests
    {
      using System;
      using NUnit.Framework;

      [TestFixture]
      public class SuccessTests
      {
        // ...
      }
    }

    Imports System
    Imports Nunit.Framework

    Namespace Nunit.Tests

      <TestFixture()> Public Class SuccessTests
        ' ...
      End Class
    End Namespace

    #using <Nunit.Framework.dll>
    using namespace System;
    using namespace NUnit::Framework;

    namespace NUnitTests
    {
      [TestFixture]
      public __gc class SuccessTests
      {
        // ...
      };
    }

    #include "cppsample.h"

    namespace NUnitTests {
      // ...
    }

    package NUnit.Tests;

    import System.*;
    import NUnit.Framework.TestFixture;

    /** @attribute NUnit.Framework.TestFixture() */
    public class SuccessTests
    {
      // ...
    }

### Parameterized Test Fixtures (NUnit 2.5)

Beginning with NUnit 2.5, test fixtures may take constructor arguments. Argument values are specified as arguments to the TestFixture attribute. NUnit will construct a separate instance of the fixture for each set of arguments.

#### Example

The following test fixture would be instantiated by NUnit three times, passing in each set of arguments to the appropriate constructor. Note that there are three different constructors, matching the data types provided as arguments.

    [TestFixture("hello", "hello", "goodbye")]
    [TestFixture("zip", "zip")]
    [TestFixture(42, 42, 99)]
    public class ParameterizedTestFixture
    {
        private string eq1;
        private string eq2;
        private string neq;

        public ParameterizedTestFixture(string eq1, string eq2, string neq)
        {
            this.eq1 = eq1;
            this.eq2 = eq2;
            this.neq = neq;
        }

        public ParameterizedTestFixture(string eq1, string eq2)
            : this(eq1, eq2, null) { }

        public ParameterizedTestFixture(int eq1, int eq2, int neq)
        {
            this.eq1 = eq1.ToString();
            this.eq2 = eq2.ToString();
            this.neq = neq.ToString();
        }

        [Test]
        public void TestEquality()
        {
            Assert.AreEqual(eq1, eq2);
            if (eq1 != null && eq2 != null)
                Assert.AreEqual(eq1.GetHashCode(), eq2.GetHashCode());
        }

        [Test]
        public void TestInequality()
        {
            Assert.AreNotEqual(eq1, neq);
            if (eq1 != null && neq != null)
                Assert.AreNotEqual(eq1.GetHashCode(), neq.GetHashCode());
        }
    }

### Generic Test Fixtures (NUnit 2.5)

Beginning with NUnit 2.5, you may use a generic class as a test fixture. In order for NUnit to instantiate the fixture, you must specify the types to be used as arguments to TestFixtureAttribute, which may now appear multiple times on the class.

#### Example

The following test fixture would be instantiated by NUnit twice, once using an ArrayList and once using a List.

    [TestFixture(typeof(ArrayList))]
    [TestFixture(typeof(List<int>))]
    public class IList_Tests<TList> where TList : IList, new()
    {
      private IList list;

      [SetUp]
      public void CreateList()
      {
        this.list = new TList();
      }

      [Test]
      public void CanAddToList()
      {
        list.Add(1); list.Add(2); list.Add(3);
        Assert.AreEqual(3, list.Count);
      }
    }

### Generic Test Fixtures with Parameters (NUnit 2.5)

If a Generic fixture, uses constructor arguments, there are three approaches to telling NUnit which arguments are type parameters and which are normal constructor parameters.

1. Specify both sets of parameters as arguments to the TestFixtureAttribute. Leading System.Type arguments are used as type parameters, while any remaining arguments are used to construct the instance. In the following example, this leads to some obvious duplication...

       [TestFixture(typeof(double), typeof(int), 100.0, 42)]
       [TestFixture(typeof(int) typeof(double), 42, 100.0)]
       public class SpecifyBothSetsOfArgs
       {
           T1 t1;
           T2 t2;

           public SpecifyBothSetsOfArgs(T1 t1, T2 t2)
           {
               this.t1 = t1;
               this.t2 = t2;
           }

           [TestCase(5, 7)]
           public void TestMyArgTypes(T1 t1, T2 t2)
           {
               Assert.That(t1, Is.TypeOf());
               Assert.That(t2, Is.TypeOf());
           }
       }

2. Specify normal parameters as arguments to TestFixtureAttribute and use the named parameter TypeArgs= to specify the type arguments. Again, for this example, the type info is duplicated, but it is at least more cleanly separated from the normal arguments...

       [TestFixture(100.0, 42, TypeArgs=new Type[] {typeof(double), typeof(int) } )]
       [TestFixture(42, 100.0, TypeArgs=new Type[] {typeof(int), typeof(double) } )]
       public class SpecifyTypeArgsSeparately
       {
           T1 t1;
           T2 t2;

           public SpecifyTypeArgsSeparately(T1 t1, T2 t2)
           {
               this.t1 = t1;
               this.t2 = t2;
           }

           [TestCase(5, 7)]
           public void TestMyArgTypes(T1 t1, T2 t2)
           {
               Assert.That(t1, Is.TypeOf());
               Assert.That(t2, Is.TypeOf());
           }
       }

3. In some cases, when the constructor makes use of all the type parameters NUnit may simply be able to deduce them from the arguments provided. That's the case here and the following is the preferred way to write this example...

       [TestFixture(100.0, 42)]
       [TestFixture(42, 100.0)]
       public class DeduceTypeArgsFromArgs
       {
           T1 t1;
           T2 t2;

           public DeduceTypeArgsFromArgs(T1 t1, T2 t2)
           {
               this.t1 = t1;
               this.t2 = t2;
           }

           [TestCase(5, 7)]
           public void TestMyArgTypes(T1 t1, T2 t2)
           {
               Assert.That(t1, Is.TypeOf());
               Assert.That(t2, Is.TypeOf());
           }
       }