If you're on Windows, there is a built-in test. I would personally recommend starting with the Windows test rather than with a video as you have no way of knowing whether the video works correctly unless you have previously viewed it in a working environment.
In Windows 8.1 and below, right mouse-click the volume icon in the System Notification area near the clock and select Playback devices. On the Playback tab, right mouse-click your headphones and select Test for a simple stereo test, You'll hear a sample sound in the left speaker first, followed by the right, if working correctly.
In Windows 10, right mouse-click the volume icon and then select Sounds, then switch to the Playback tab in the Sound dialog. The rest of the...