Pavucontrol Mixing

This test case tests that various audio outputs can be mixed and sent to different devices using Pavucontrol.

Setup

This test case should be performed on bare-metal machines. To be able to test with virtual machines, consider a USB device pass-through. Specify in the comments if you used the VM for this test.
The computer must be equipped with at least two sound devices.
Install a desktop version of Fedora 34 (or later).
Install the pavucontrol package.
Connect your speakers (headphones) to all your computer’s sound devices, i.e. each sound device should have its own speakers connected when performing this test case.

Start Pavucontrol.
Go to the Output Devices tab and check that all your audio devices are listed there.
Start two (or more) different applications that play audio. Alternatively, you can open two or more Youtube videos in Firefox.
Go to the Playback tab and confirm that all sound playing applications appear listed there.
Adjust the output volume for each playing application using the corresponding volume slider. Check that each of the outputs can be adjusted independently and that you can mix the final sound output to your likings.
Use the Mute audio button to mute the selected application output. Check that the channel is muted and does not produce any audible sound.
Unmute the channel and check that the sound is audible again.
Click on Lock channels together button and unlock the left and right audio channel. Check that the volume can be adjusted for each channel separately. Try this with all application's outputs.
For each playing applications, click on the button showing the current device on the right side of the panel and select a different device to output the application sound. Confirm that the application's output stops playing on the current device and starts playing on the newly selected device.