Real-time voice or video communication between users on mobile devices or computers
"Test call" option is not available in Teams with Personal account (Teams Free). This feature is only available in Teams with a Business account.
In Teams Free you can use the virtual "Echo / Sound Test Service" contact to test your audio/video settings.
However, you should also check if your microphone is working with any other application and if the device on which you are using Teams have granted permission to use Microphone with Teams.