Simulate audio device for running tests on GitHub Actions

[orhun]

Is your feature request related to a problem? Please describe.

Currently we can't run the audio tests on a GitHub runner since it requires a audio device to be present:

ALSA lib confmisc.c:855:(parse_card) cannot find card '0'
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_card_inum returned error: No such file or directory
ALSA lib confmisc.c:422:(snd_func_concat) error evaluating strings
test app::tests::test_handle_key_event ... FAILED

failures:

---- app::tests::test_handle_key_event stdout ----
Error: Stream(DefaultStreamConfigError(DeviceNotAvailable))
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory
ALSA lib confmisc.c:1334:(snd_func_refer) error evaluating name
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:5701:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2664:(snd_pcm_open_noupdate) Unknown PCM default


failures:
    app::tests::test_handle_key_event

test result: FAILED. 4 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.11s

Describe the solution you'd like

Either simulate an audio device (or create it virtually) for running the tests like this:

cargo test --features audio-tests

Describe alternatives you've considered

Update the existing tests for running without an audio device - e.g. create mock objects for sinks etc.

Additional context

• See the test step here: https://github.com/orhun/daktilo/blob/main/.github/workflows/ci.yml
• audio-tests live in this module: https://github.com/orhun/daktilo/blob/main/src/app.rs