For instructions on testing your video for your specific device, as well as information about the various Video Settings in Zoom, see How Do I Test My Video? in the Zoom Help Center.
You can also launch a test Zoom meeting anytime at zoom.us/test. This will launch a meeting where you are the only participant (you can then invite others if desired). This option allows you to test your audio and video even if you don't have the Zoom desktop client installed and plan to host or attend a meeting or webinar through your web browser, such as Google Chrome. If you do have the desktop client installed, zoom.us/test will open the test meeting in the client, just like it does for a normal meeting or webinar.