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Writing and running your first unit test in C#

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 of unit tests that use the C# API to isolate.

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

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:

using System.Windows.Forms;
using TypeMock.ArrangeActAssert;

Add the Isolated attribute to the test class:

[TestClass, Isolated]
public class Test0_Tutorial

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:

 

  • 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

 

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

 

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:

 

Read our blog to see more advanced usages of Isolator and unit testing information.

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