If your Mac is running slowly, crashing, or just generally misbehaving, and you’re not entirely sure what the problem is, one good option is to use Check Computer. Running Check Computer will queue up the full suite of Techtool Pro’s tests, systematically checking the various components components in your Mac, looking for potential problems. At the conclusion of the test, a report will display the results, giving you a good idea about what what the next steps might be.
Check Computer – Starting Point for Diagnostic Testing
For general troubleshooting, choose the Tests icon, and then choose Check Computer, if it isn’t already selected. Click Run Check Computer. While the complete suite of tests can take a while, it will be the most complete set of tests you can run outside of an Apple Store.

Check Computer – Testing in Progress

If you’re pretty sure the problem doesn’t involve a particular component, you can use the Configure button to specify which tests to be run, or specify which drives should be tested with the drive-specific tests.
Configure Check Computer

If you’re uncertain where the problem lies, Techtool Pro’s Check Computer suite can identify what hardware component might be to blame. If all tests pass, then the issue might be software related. Either way, using one of Techtool Pro’s tools may be helpful for further troubleshooting.
For more information about using Techtool Pro’s tests and tools: