There is no one stop diagnostic tool for laptops (or any computer hardware really). The vendor sometimes provides a boot disk that checks for components, but every one I have seen will only run on specific hardware. There are some generic tools to check for issues such as memtest, scandisk, Prime95, but almost all except memtest need you to be able to get to Windows to run them.
Does the laptop just stop responding, does it shut off, do you get video corruption? Have you swapped out the battery and power supply? Fans all working? Try different RAM or hard drive? If you don't have diagnostic software for your model that you can boot off, or runs in your BIOS, you may need to just try swapping out some hardware. Although wherever you took it to be checked already should have done that for you.