In this page of ReSharper options, you can adjust unit testing settings related to MSTest tests.
|Enable MSTest support||By default, ReSharper adds action indicators allowing you to execute MSTest tests right from the editor and automatically discovers MSTest tests in your solution. Clear this check box to disable this behavior.|
|Select Test Setting File|| |
This field allows you to choose a custom test settings configuration (.testsettings file within your solution).
For more information on MSTest test settings, see MSDN. Specifying Test Settings for Visual Studio Tests