dotCover shares the unit test support with another JetBrains .NET developer tool,
ReSharper. These two tools have the same
unit test runner engines as well as Unit Test Explorer and
Unit Test Sessions windows.
If you install dotCover after ReSharper, dotCover disables its own unit test runner
so that you can continue using ReSharper's unit test commands and windows;
all additional dotCover commands are integrated in ReSharper menus.
However, if you decide to uninstall ReSharper later, the unit test support will be automatically enabled in dotCover after you restart Visual Studio.
If you disable ReSharper, dotCover does not switch on its unit test support automatically; you need to enable it manually as described below.
To see whether the test runner is disabled, check if the dotCover | Unit Tests submenu of the main menu is grayed out. If you have not changed any settings and the unit tests are disabled, it means that ReSharper is installed on your computer. It can take care of unit tests and dotCover commands are integrated into ReSharper's menu: ReSharper | Unit Tests.
Anytime, you can explicitly enable unit test runner in dotCover. To do so, tick the Enable Unit Testing check-box in the dotCover Options | Unit Testing. For more information, see Configuring Unit Test Support.
Once you have changed this option, dotCover will not automatically enable or disable unit test runner if you install or uninstall ReSharper.
You should also notice that test engines of ReSharper and dotCover are configured separately and may have different settings and unit test plugins. For more information, see Configuring Unit Test Support.