/usr/share/doc/nunit/html/testFixture.html

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<h3>TestFixtureAttribute (NUnit 2.0 / 2.5)</h3>

<p>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.</p>
	
<p>Most restrictions on a class that is used as a test fixture have now been
   eliminated. As of NUnit 2.5.3, a test fixture class:
	<ul>
		<li>May be public, protected, private or internal.
		<li>May be a static class in .NET 2.0 or later.
		<li>May be generic, so long as any type parameters are provided or
		    can be inferred from the actual arguments.
		<li>May not be abstract - although the attribute may be applied to an
		    abstract class intended to serve as a base class for test fixtures.
		<li>If no arguments are provided with the TestFixtureAttribute, the class
		     must have a default constructor. 
		<li>If arguments are provided, they must match one of the constructors.
	</ul>
</p>

<p>If any of these restrictions are violated, the class is not runnable
   as a test and will display as an error.</p>

<p>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.</li>

<p>Beginning with NUnit 2.5, the <b>TestFixture</b> attribute is optional
   for non-parameterized, non-generic fixtures. So long as the class contains
   at least one method marked with the <b>Test</b>, <b>TestCase</b> or 
   <b>TestCaseSource</b> attribute, it will be treated as a test fixture.

<h4>Example:</h4>

<div class="code">

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<pre class="cs">namespace NUnit.Tests
{
  using System;
  using NUnit.Framework;

  [TestFixture]
  public class SuccessTests
  {
    // ...
  }
}
</pre>

<pre class="vb">Imports System
Imports Nunit.Framework

Namespace Nunit.Tests

  &lt;TestFixture()&gt; Public Class SuccessTests
    ' ...
  End Class
End Namespace
</pre>

<pre class="mc">#using &lt;Nunit.Framework.dll&gt;
using namespace System;
using namespace NUnit::Framework;

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

#include "cppsample.h"

namespace NUnitTests {
  // ...
}
</pre>

<pre class="js">package NUnit.Tests;

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


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

</div>

<h3>Inheritance</h3>

<p>The <b>TestFixtureAttribute</b> may be applied to a base class and is
inherited by any derived classes. This includes any abstract base class,
so the well-known Abstract Fixture pattern may be implemented if desired.

<p>In order to facilitate use of generic and/or parameterized classes,
where the derived class may require a different number of arguments (or
type arguments) from the base class, superfluous <b>TestFixture</b> 
attributes are ignored, using the following rules:

<ol>
<li>If all TestFixture attributes provide constructor or type arguments, 
then all of them are used.
<li>If some of the attributes provide arguments and others do not, then
only those with arguments are used and those without arguments are ignored.
<li>If none of the attributes provide arguments, one of them is selected
for use by NUnit. It is not possible to predict which will be used, so
this situation should generally be avoided.
</ol>

This permits code like the following, which would cause an error if the
attribute on the base class were not ignored.

<div class="code">
<pre>[TestFixture]
public class AbstractFixtureBase
{
    ...
}

[TestFixture(typeof(string))]
public class DerivedFixture&lt;T&gt; : AbstractFixtureBase
{
    ...
}
</pre>
</div>

<h3>Parameterized Test Fixtures (NUnit 2.5)</h3>

<p>Beginning with NUnit 2.5, test fixtures may take constructor arguments.
   Argument values are specified as arguments to the <b>TestFixture</b>
   attribute. NUnit will construct a separate instance of the fixture
   for each set of arguments.
   
<p>Individual fixture instances in a set of parameterized fixtures may be ignored. 
   Set the <b>Ignore</b> named parameter of the attribute to true or set 
   <b>IgnoreReason</b> to a non-empty string.

<p>Individual fixture instances may be given categories as well. Set the <b>Category</b>
   named parameter of the attribute to the name of the category or to a comma-separated
   list of categories.
   
<h4>Example</h4>

<p>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.
   
<div class="code"><pre>
[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 &amp;&amp; eq2 != null)
            Assert.AreEqual(eq1.GetHashCode(), eq2.GetHashCode());
    }

    [Test]
    public void TestInequality()
    {
        Assert.AreNotEqual(eq1, neq);
        if (eq1 != null &amp;&amp; neq != null)
            Assert.AreNotEqual(eq1.GetHashCode(), neq.GetHashCode());
    }
}
</pre></div>

<h3>Generic Test Fixtures (NUnit 2.5)</h3>

<p>Beginning with NUnit 2.5, you may also use a generic class as a test fixture.
   In order for NUnit to instantiate the fixture, you must either specify the 
   types to be used as arguments to <b>TestFixtureAttribute</b> or use the
   named parameter <b>TypeArgs=</b> to specify them. NUnit will construct a
   separate instance of the fixture for each <b>TestFixtureAttribute</b> 
   you provide.
   
<h4>Example</h4>

<p>The following test fixture would be instantiated by NUnit twice,
   once using an ArrayList and once using a List&lt;int&gt;.
   
<div class="code"><pre>
[TestFixture(typeof(ArrayList))]
[TestFixture(typeof(List&lt;int&gt;))]
public class IList_Tests&lt;TList&gt; 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);
  }
}</pre></div>

<h3>Generic Test Fixtures with Parameters (NUnit 2.5)</h3>

<p>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.
   <ol>
   <li>Specify both sets of parameters as arguments to the <b>TestFixtureAttribute</b>.
       Leading <b>System.Type</b> 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...

<div class="code"><pre>
[TestFixture(typeof(double), typeof(int), 100.0, 42)]
[TestFixture(typeof(int) typeof(double), 42, 100.0)]
public class SpecifyBothSetsOfArgs&lt;T1, T2&gt;
{
    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&lt;T1&gt;());
        Assert.That(t2, Is.TypeOf&lt;T2&gt;());
    }
}</pre></div>

   <li>Specify normal parameters as arguments to <b>TestFixtureAttribute</b>
       and use the named parameter <b>TypeArgs=</b> 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...

<div class="code" style="width: 40em"><pre>
[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&lt;T1, T2&gt;
{
    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&lt;T1&gt;());
        Assert.That(t2, Is.TypeOf&lt;T2&gt;());
    }
}</pre></div>

   <li>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...
   
<div class="code"><pre>
[TestFixture(100.0, 42)]
[TestFixture(42, 100.0)]
public class DeduceTypeArgsFromArgs&lt;T1, T2&gt;
{
    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&lt;T1&gt;());
        Assert.That(t2, Is.TypeOf&lt;T2&gt;());
    }
}</pre></div>
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