Writing and running your first unit test in C# 

 You can find the code used in this tutorial in Test0_Tutorial.cs, in the Isolator installation folder (usually C:Program FilesTypemockIsolatorVERSION), under the Typemock.Example.CSharp solution.

Step 1 - Create a new Test Project

This step shows you how to create a new test project in Visual Studio, and add the Typemock references you need.

• Open Visual Studio, click ‘File’ and create a new Test Project.

  

• Right click project ‘References’, click ‘Add References’ and add ‘‘Typemock Isolator core DLL’ and ‘Typemock Isolator C# API’

For this example test, you’ll need a reference to System.Windows.Forms as well.

Step 2 - Write unit tests

This section will walk you through the three stages in unit tests that use the C# API to isolate.

     1. Arrange – Set up your faked object’s behaviour

     2. Act - Call your test code

     3. Assert - Make sure that the tests were called

In the new test project we opened in Visual Studio, go to UnitTest1.cs in the ‘Solutions’ column and add the following test code to the beginning of the file:

Add the Isolated attribute to the test class:

Example Test 1 - Simple test using MessageBox

This example shows how to ignore a method call, and verify it was called during our test.

We’ll use the following APIs in this test:

• Isolate.WhenCalled - The method inside the WhenCalled clause will be ignored, and will return a fake value
• Isolate.Verify.WasCalledWithExactArguments - Verifies that the method inside the WhenCalled clause was called during the test with the exact arguments

The following takes place in the code:

[TestMethod]
public void SimpleTestUsingMessageBox()
{
 / Arrange
1 Isolate.WhenCalled(()=>MessageBox.Show(String.Empty)).WillReturn(DialogResult.OK);

 / Act
2 MessageBox.Show("This is a message"); 

 / Assert
3 Isolate.Verify.WasCalledWithExactArguments(()=>MessageBox.Show("This is a message"));
}

• Set all calls to MessageBox.Show to be ignored, and return a fake value.
• Call MessageBox.Show - notice that when you run the test, the MessageBox doesn't actually appear.
• Check that the static function ‘Show’ was called during the test with the parameter "This is a message".

  Example Test 2 - Complex Test

This example shows how to test the interaction between two classes:

• SomeClass - Has a static method called MyMethod
• UserOfSomeClass - Has a method called DoSomething

public class SomeClass
{
 public static void MyMethod()
 {
  / do work
 }
}

public class UserOfSomeClass
{
 public void DoSomething()
 {
  try

  {
   SomeClass.MyMethod();
  }
 catch (Exception exc)
 {
  MessageBox.Show("Exception caught: " + exc.Message);
  }
 }
}

This test checks that the user sees every exception thrown from SomeClass using a MessageBox.

The following APIs are used in the test:

We’ll use the following APIs in this test:

• Isolate.WhenCalled(..).WillThrow - The method inside the WhenCalled clause will throw a specified exception when called
• Isolate.WhenCalled(..).WillReturn - The method inside the WhenCalled will be ignored, and return a fake value
• Isolate.Verify.WasCalledWithExactArguments - Verifies that the method inside the WhenCalled clause was called with the exact arguments during the text execution

[TestMethod]
public void ComplexTest()
{
 / Arrange
1a Isolate.WhenCalled(()=> SomeClass.MyMethod()).WillThrow( new Exception("foo"));
2a Isolate.WhenCalled(()=>MessageBox.Show(String.Empty)).WillReturn(DialogResult.Cancel);

 / Act
2 UserOfSomeClass user = new UserOfSomeClass();
user.DoSomthing(); 

 / Assert
3 Isolate .Verify.WasCalledWithExactArguments(()=> MessageBox .Show("Exception caught: foo"));
}

The following takes place in the code:

• The actual test code - Create a new instance of UserOfSomeClass and call the DoSomething method.
• Check that MessageBox.Show was called during our test with ‘Exception caught: foo’.

Here is the full source code we used in our examples:

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Windows.Forms;
using TypeMock.ArrangeActAssert;


[TestClass, Isolated]
public class Test0_Tutorial

{

 [TestMethod]
 public void SimpleTestUsingMessageBox()
 {
  / Arrange
  Isolate.WhenCalled(()=>MessageBox.Show(String.Empty)).WillReturn(DialogResult.OK);

  / Act
  MessageBox.Show("This is a message"); 

  / Assert
  Isolate.Verify.WasCalledWithExactArguments(()=> MessageBox.Show("This is a message"));
 }

 [TestMethod]
 public void ComplexTest()
 {
  / Arrange
  Isolate.WhenCalled(()=> SomeClass.MyMethod()).WillThrow( new Exception("foo"));
  Isolate.WhenCalled(()=> MessageBox.Show(String.Empty)).WillReturn( DialogResult.Cancel);

  / Act
  UserOfSomeClass user = new UserOfSomeClass ();
  user.DoSomething(); 

  / Assert
  Isolate.Verify.WasCalledWithExactArguments(()=>MessageBox.Show("Exception caught:
  foo"));
 }


}


public class SomeClass
{
 public static void MyMethod()
 {
  / do work
 }
}

public class UserOfSomeClass
{
 public void DoSomething()
 {
  try
  {
   SomeClass.MyMethod();
  }
  catch ( Exception exc)
  {
   MessageBox .Show("Exception caught: " + exc.Message);
  }
 }
}

For more help on using Typemock Isolator, read the following:

• Isolator AAA API - The Basics
• Creating fakes
• Setting behaviour
• Verification

You’re also invited to read our blog to see more advanced usages of Isolator and unit testing information, and if you have any questions, feel free to use our support forums.