Run the Compile all classes on the Apex Classes page in Setup to compile all the Apex classes in your organization. If you have classes that are installed from a managed package and that have test methods or are test classes, you must compile these classes first before you can view them and run their test methods from the Apex Test Execution page. Managed package classes can be compiled only through the Compile all classes link because they cannot be saved. Otherwise, saving Apex classes that aren’t from a managed package causes them to be recompiled. This link compiles all the Apex classes in your organization, whether or not they are from a managed package
