If all test cases in the test case screen have a test result category, the tester has completed the test run.
He can click the Finish button in the last test case to finish the test run and a popup appears to return to his test run overview.
When he clicks the Finish button in the last test case, but hasn't run all test cases, a pop-up will appear to alert him that he's not finished yet.
The tester can choose Cancel to proceed with running the test or choose Back to overview to quit the test and go back to his test run overview. He can resume the test run at a later time.