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October 25, 2009

Unit Testing: Code Coverage

Filed under: C#,Testing,VB.NET @ 6:27 pm

Visual Studio 2008 (Team System ONLY) provides a really nice set of tools for viewing the code coverage of your unit tests.

NOTE: While Visual Studio 2008 Professional Edition has tools for building, executing, and debugging unit tests, it does NOT include the code coverage tools.

[To begin with an overview of unit testing, start here.]

Code coverage illustrates how much of the code was executed (or covered) by the unit tests.

NOTE: This post assumes you have already generated or created at least one unit test.

To view the code coverage for your unit tests:

1) Enable code coverage in the test run configuration file.

When you create your first unit test, Visual Studio adds a LocalTestRun.testrunconfig file to your solution under the Solution Items folder. Double-click on this file to open it:

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Select Code Coverage from the left list:

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Select the files on the right that you wish to view code coverage. Don’t pick your test projects; rather pick the projects containing the code that is being tested. Then click Apply and Close.

2) Run your unit tests. The Test Results dialog appears.

See this prior post for more information on executing unit tests.

Your results should appear similar to the following:

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3) If the tests pass, click the Show Code Coverage Results button in the far upper right corner of the Test Results dialog. The Code Coverage Results dialog appears.

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This dialog displays all of the code in all of the files you selected for code coverage instrumentation. Drill down as needed to find the desired code.

In this case, the unit test is testing the getter and setter for the LastName. Notice  that the covered percentage for both the getter and setter is 100%. That means that the unit test is executing every line of code in the getter and setter.

4) Double click on any item in the Code Coverage dialog to open the associated code window.

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Notice how the code is color-coded. Blue shows code that was executed by the unit test. Red shows code that was not executed.

Use this feature to ensure you have unit tests for each unit of your code.

Enjoy!

EDITED 10/27/09: While Visual Studio 2008 Professional Edition has tools for building, executing, and debugging unit tests, it does NOT include the code coverage tools. In the original version of this post, I incorrectly stated that code coverage tools were available in the Professional Edition. This post has been corrected.

5 Comments

  1.   Patryk Zera — October 27, 2009 @ 7:22 am    Reply

    I have VS 2008 Professional, but I don’t see Code Coverage in LocalTestRun.testrunconfig (also I don’t have Controller And Agent and Web Test options). Do I need test certain projects or install something additional?

  2.   DeborahK — October 27, 2009 @ 10:48 am    Reply

    Hi Patryk –

    My mistake. The Professional Edition has the tools for building, executing, and debugging unit tests. However, the code coverage tools are only in the Team System Edition.

    I corrected the post.

    Thank you *very* much for pointing this out so I could correct this error.

  3.   Patryk Zera — October 28, 2009 @ 6:38 am    Reply

    Thank you for taking your time to investigate this.

  4.   Roger Pearse — November 17, 2009 @ 1:11 pm    Reply

    I must admit I’m getting disillusioned with the unit test features in VS2008. It’s way more complex than JUnit, and seems buggy. Try debugging from a test — often you can’t step into the code called. It may be OK on a brand-new project, but when converting a mass of VB6 and adding tests, it just fails.

  5.   DeborahK — November 17, 2009 @ 3:08 pm    Reply

    I have a *very large* solution that originally was converted from VB6. In general, I am able to debug from the tests with no problem.

    However, if I have been debugging from within the tests for a significant amount of time (like all afternoon), I then find that I have difficulty. Often just existing Visual Studio and reopening the solution solves the issues and allows me to continue.

    Hope this helps.

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