ClassInitializeAttribute Class

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.SmartDevice.UnitTestFramework (in Microsoft.VisualStudio.SmartDevice.UnitTestFramework.dll)

Syntax

'Declaration
<AttributeUsageAttribute(AttributeTargets.Method, AllowMultiple := False)> _
Public NotInheritable Class ClassInitializeAttribute _
    Inherits Attribute

'Usage
Dim instance As ClassInitializeAttribute

[AttributeUsageAttribute(AttributeTargets.Method, AllowMultiple = false)]
public sealed class ClassInitializeAttribute : Attribute

[AttributeUsageAttribute(AttributeTargets::Method, AllowMultiple = false)]
public ref class ClassInitializeAttribute sealed : public Attribute

public final class ClassInitializeAttribute extends Attribute

Remarks

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.

Important Note:
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.

Examples

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.

using System;

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

Imports System

Namespace SampleClassLib
    Public Class DivideClass
        Shared Function DivideMethod(ByVal denominator As Integer) As Integer
            Return 2 \ denominator
        End Function
    End Class
End Namespace

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.

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);
        }
    }
}

Imports Microsoft.VisualStudio.TestTools.UnitTesting
Imports SampleClassLib2.SampleClassLib
Imports System
Imports System.IO
Imports System.Windows.Forms

Namespace TestNamespace
    <TestClass()> _
    Public NotInheritable Class DivideClassTest
        <AssemblyInitialize()> _
        Public Shared Sub AssemblyInit(ByVal context As TestContext)
            MsgBox("AssemblyInit " + context.TestName)
        End Sub 'AssemblyInit

        <ClassInitialize()> _
        Public Shared Sub ClassInit(ByVal context As TestContext)
            MsgBox("ClassInit " + context.TestName)
        End Sub 'ClassInit

        <TestInitialize()> _
        Public Sub Initialize()
            MsgBox("TestMethodInit")
        End Sub 

        <TestCleanup()> _
        Public Sub Cleanup()
            MsgBox("TestMethodCleanup")
        End Sub 

        <ClassCleanup()> _
        Public Shared Sub ClassCleanup()
            MsgBox("ClassCleanup")
        End Sub 

        <AssemblyCleanup()> _
        Public Shared Sub AssemblyCleanup()
            MsgBox("AssemblyCleanup")
        End Sub

        <TestMethod()> _
        <ExpectedException(GetType(System.DivideByZeroException))> _
        Public Sub DivideMethodTest()
            DivideClass.DivideMethod(0)
        End Sub
    End Class
End Namespace

Inheritance Hierarchy

System.Object
  System.Attribute
    Microsoft.VisualStudio.TestTools.UnitTesting.ClassInitializeAttribute

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

See Also

Reference

ClassInitializeAttribute Members

Microsoft.VisualStudio.TestTools.UnitTesting Namespace

Other Resources

Anatomy of a Unit Test

Unit Testing Framework