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ClassInitializeAttribute Class

Visual Studio 2005

Identifies a method that contains code that must be used before any of the tests in the test class have run and to allocate resources to be used by the test class. This class cannot be inherited.

Namespace: Microsoft.VisualStudio.TestTools.UnitTesting
Assembly: Microsoft.VisualStudio.QualityTools.UnitTestFramework (in microsoft.visualstudio.qualitytools.unittestframework.dll)

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[AttributeUsageAttribute(AttributeTargets.Method, AllowMultiple=false)] 
public sealed class ClassInitializeAttribute : Attribute
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/** @attribute AttributeUsageAttribute(AttributeTargets.Method, AllowMultiple=false) */ 
public final class ClassInitializeAttribute extends Attribute
JScript
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AttributeUsageAttribute(AttributeTargets.Method, AllowMultiple=false) 
public final class ClassInitializeAttribute extends Attribute

When run in a load test, the method marked with this attribute will run once, and any initialization operations it performs will apply to the entire test. If you need to do initialization operations once for every virtual user iteration in the test, use the TestInitializeAttribute.

The order that methods will be run is:

  1. Methods marked with the AssemblyInitializeAttribute.

  2. Methods marked with the ClassInitializeAttribute.

  3. Methods marked with the TestInitializeAttribute.

  4. Methods marked with the TestMethodAttribute.

Only one method in a class may be decorated with this attribute.

NoteImportant

This attribute should not be used on ASP.NET unit tests, that is, any test with [HostType("ASP.NET")] attribute. Because of the stateless nature of IIS and ASP.NET, a method decorated with this attribute may be called more than once per test run.

This attribute can be specified on a method. Only one instance of this attribute may be applied to a method.

For more information about how to use attributes, see Extending Metadata Using Attributes.

The following examples demonstrate the initialization and clean-up attributes used to indicate which methods should be run by the test engine at different periods of the test.

The first code samples contain a class and method to test. To run this example, create a class library project and replace the code with the following example.

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using System;

namespace SampleClassLib
{
    public class DivideClass
    {
        public static int DivideMethod(int denominator)
        {
            return (2 / denominator);
        }
    }
}

The following example contains code to test DivideMethod() found in the previous code examples. Create a test project and put the following code in a test class document. Add the appropriate references to the project. This code contains attributes that control the initialization and clean-up execution order for the method, class, and assembly.

In particular, note the ClassInitialize attribute on the ClassInit()method.

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using Microsoft.VisualStudio.TestTools.UnitTesting;
using SampleClassLib;
using System;
using System.Windows.Forms;

namespace TestNamespace
{
    [TestClass()]
    public sealed class DivideClassTest
    {
        [AssemblyInitialize()]
        public static void AssemblyInit(TestContext context)
        {
            MessageBox.Show("AssemblyInit " + context.TestName);
        }

        [ClassInitialize()]
        public static void ClassInit(TestContext context)
        {
            MessageBox.Show("ClassInit " + context.TestName);
        }

        [TestInitialize()]
        public void Initialize()
        {
            MessageBox.Show("TestMethodInit");
        }

        [TestCleanup()]
        public void Cleanup()
        {
            MessageBox.Show("TestMethodCleanup");
        }

        [ClassCleanup()]
        public static void ClassCleanup()
        {
            MessageBox.Show("ClassCleanup");
        }

        [AssemblyCleanup()]
        public static void AssemblyCleanup()
        {
            MessageBox.Show("AssemblyCleanup");
        }

        [TestMethod()]
        [ExpectedException(typeof(System.DivideByZeroException))]
        public void DivideMethodTest()
        {
            DivideClass.DivideMethod(0);
        }
    }
}
System.Object
   System.Attribute
    Microsoft.VisualStudio.TestTools.UnitTesting.ClassInitializeAttribute
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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Annotations FAQ
ClassInitialize vs Constructor
The ClassInitialize method is static and runs once (with the first instance of the test class)
The constructor is obviously not static and runs with each initialization of the test class (which is one per test method)

For more information see:
http://blogs.msdn.com/b/nnaderi/archive/2007/02/17/explaining-execution-order.aspx
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Why use this instead of a constructor?
I don't understand why you would use this instead of a class constructor. Don't they have the same effects? What are the differences?

[tfl - 03 08 09] Hi - and thanks for your post. You should post questions like this to the MSDN Forums at http://forums.microsoft.com/msdn or the MSDN Newsgroups at

http://www.microsoft.com/communities/newsgroups/en-us/. You are much more likely get a quicker response using the forums than through the Community Content. For specific help about:
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