A frequent concern with writing unit tests with MSTest is how to include additional files and test data for a test run. This process has changed between Visual Studio 2010 and 2012 and it’s become a source of confusion.
With Visual Studio 2010 and earlier, every time you ran your tests Visual Studio would copy all files related to the test to a test run folder and execute them from this location. For local development this feature allows you to compare results between test runs, but the feature is also intended to support deploying the tests to remote machines for execution.
If your tests depend on additional files such as external configuration files or 3rd party dependencies that aren’t directly referenced by the tests, you would need to enable Deployment in your testsettings and then either specifying the deployment items in the testsettings file or marking each test with a DeploymentItemAttribute.
What’s changed in Visual Studio 2012?
Visual Studio 2012 has a number of changes related to the test engine that impact deployment. The most visible change is that Visual Studio 2012 no longer automatically adds the testsettings file to your solution when you add a Test project. The testsettings file can be added to your project manually, but it’s generally recommended that you don’t use it as it’s for backward compatibility and not all features within Visual Studio 2012 are backward compatible. Microsoft Fakes for example are not backward compatible.
The biggest change related to deployment is that Visual Studio 2012 tests run directly out of the output folder by default. This adds a significant speed boost for the tests but it also means that if your tests are dependent on files that are already part of the build output, you won’t need to enable deployment at all.
Another interesting change is that if you include a DeploymentItemAttribute in your tests, Deployment will be automatically enabled and your tests will run out of the deployment folder.
More information can be found here.