Am developing an existing iOS application and I have to write unit test cases for this project. It is building and running in Simulator 6.0. Whenever I try to test t
You must have changed your product name. Due to mis-match of your workspace name and product(application)name this error occurs.
You just need to replace the workspace name to product(application) name in the TEST HOST Build settings of the ProjectName-Tests targe as stated in the image. To catch up that, select to ProjectName-Tests target, select Build Settings, search for the Test Host term.

This is the standard configuration solution for this error.
Cheers!!