Could not run tests on class 01p... because: connection was cancelled here

Go to--> Apex Text Execution 

1. After clicking Options..., check Disabled Parallel Apex Testing
2. And then clicked the link "View Test History"  -->  Clear Test Results.

Then go to  Develop --> Apex Classes and

1. Click "Compile all classes"
2. Then click "Estimate your organization's code coverage"
3. And finally,  Run All Tests