title: How to use ApprovalTests on Teamcity?
body: <p>I am using <a href="http://blog.approvaltests.com/" rel="noreferrer">Approval Tests</a>. On my dev machine I am happy with <code>DiffReporter</code> that starts <strong>TortoiseDiff</strong> when my test results differ from approved:</p>
  
  <pre><code>    [UseReporter(typeof (DiffReporter))]
      public class MyApprovalTests
      { ... }
  </code></pre>
  
  <p>However when the same tests are running on Teamcity and results are different tests fail with the following error:</p>
  
  <pre><code>System.Exception : Unable to launch: tortoisemerge.exe with arguments ...
  Error Message: The system cannot find the file specified
  ---- System.ComponentModel.Win32Exception : The system cannot find the file 
                                                                   specified
  </code></pre>
  
  <p>Obviously it cannot find tortoisemerge.exe and that is fine because it is not installed on build agent. But what if it gets installed? Then for each fail another instance of tortoisemerge.exe will start and nobody will close it. Eventually tons of tortoisemerge.exe instances will kill our servers :)</p>
  
  <p>So the question is -- how tests should be decorated to run Tortoise Diff on local machine
  and just report errors on build server? I am aware of  <code>#IF DEBUG [UseReporter(typeof (DiffReporter))]</code> but would prefer another solution if possible.</p>