Overview / Goal

The goal was to create a testing framework which utilizes the VirtualBox Validation Kit to test the VirtualBox audio stack.

That framework must be runnable on all host/guest combinations together with all audio drivers ("backends") and device emulations being offered. This makes it a rather big testing matrix which therefore has to be processed in an automated fashion.

Additionally it should be flexible enough to add more (custom) tests lateron.

Current status / limitations

• The following test types are currently implemented:

  • Test tone (sine wave) playback from the guest
  • Test tone (sine wave) recording by the guest (injected from the host)

• Only the HDA device emulation has been verified so far.
• Only the ALSA audio stack on Debian 10 has been verified so far. Note: This is different from PulseAudio using the ALSA plugin!

Operation

The framework consists of several components which try to make use as much of the existing audio stack code as possible. This allows the following operation modes:

• Standalone: Playing back / recording audio data (test tones / .WAV files) in a standalone scenario, i.e. no VirtualBox / VMs required). This mode is using the audio (mixing) stack and available backend drivers without the need of VirtualBox being installed.
• Manual: Performing single / multiple tests manually on a local machine. Requires a running and set up test VM.
• Automated: Performs single / multiple tests via the Validation Kit audio test driver and can be triggered via the Validation Kit Test Manager. The test driver can be found at [1].
• (Re-)validation of previously ran tests: This takes two test sets and runs the validation / analysis on them. See VKAT's "verify" sub command for more.
• Self testing mode: Performs standalone self tests to verify / debug the involved components. See VKAT's "selftest" sub command for more.

[1] src/VBox/ValidationKit/tests/audio/tdAudioTest.py

Components and Terminology

The following components are in charge for performing the audio tests (depends on the operation mode, see above):

• VKAT ("Validation Kit Audio Test", also known as VBoxAudioTest): A binary which can perform the standalone audio tests mentioned above, as well as acting as the guest and host service(s) when performing manual or automated tests. It also includes the analysis / verification of audio test sets. VKAT also is included in host installations and Guest Additions since VirtualBox 7.0 to give customers and end users the opportunity to test and verify the audio stack.

  Additional features include:

  • Automatic probing of audio backends ("--probe-backends")
  • Manual playback of test tones ("play -t")
  • Manual playback of .WAV files ("play <WAV-File>")
  • Manual recording to .WAV files ("recording <WAV-File>")
  • Manual device enumeration (sub command "enum")
  • Manual (re-)verification of test sets (sub command "verify")
  • Self-contained self tests (sub command "selftest")

  See the syntax help ("--help") for more.

• ATS ("Audio Testing Service"): Component which is being used by VKAT and the Validation Kit audio driver (backend) to communicate across guest and host boundaries. Currently using a TCP/IP transport layer. Also works with VMs which are configured with NAT networking ("reverse connection").

• Validation Kit audio test driver (tdAudioTest.py): Used for integrating and invoking VKAT for manual and automated tests via the Validation Kit framework (Test Manager). Optional.

• Validation Kit audio driver (backend): A dedicated audio backend which communicates with VKAT running on the same host to perform the actual audio tests on a VirtualBox installation. This makes it possible to test the full audio stack on a running VM without any additional / external tools.

  On guest playback, data will be recorded, on guest recording, data will be injected from the host into the audio stack.

• Test sets contain

  • a test manifest with all information required (vkat_manifest.ini)
  • the generated / captured audio data (as raw PCM)

  and are either packed as .tar.gz archives or consist of a dedicated directory per test set.

  There always must be at least two test sets - one from the host side and one from the guest side - to perform a verification.

  Each test set contains a test tag so that matching test sets can be identified.

The above components are also included in VirtualBox release builds and can be optionally enabled (disabled by default).

Workflow for a single test

When a single test is being executed on a running VM, the following (simplified) workflow applies:

• VKAT on the host connects to VKAT running on the guest (via ATS, also can be a remote machine in theory).
• VKAT on the host connects to Validation Kit audio driver on the host (via ATS, also can be a remote machine in theory).

• For example, when doing playback tests, VKAT on the host ...

  • ... tells the Validation Kit audio driver to start recording

    guest playback.

  • ... tells the VKAT on the guest to start playing back audio data.

  • ... gathers all test data (generated from/by the guest and recorded from

    the host) as separate test sets.

  • ... starts verification / analysis of the test sets.

Setup instructions

• VM needs to be configured to have audio emulation and audio testing enabled (via extra-data, set "VBoxInternal2/Audio/Debug/Enabled" to "true").

• Audio input / output for the VM needs to be enabled (depending on the test).

• VKAT needs to be running on the guest and be able to connect to the host via TCP/IP.

  Note: Depending on the VM's networking configuration there might be further

  steps necessary in order to be able to reach the host from the guest. See the VirtualBox manual for more information.

Performing a manual test

• Follow "Setup instructions".
• Start VKAT on the guest (in "guest mode", e.g. "test --mode guest").
• Start VKAT on the host (in "host mode", e.g. "test --mode host") with selected test(s).
• By default the test verification will be done automatically after running the tests.

Performing manual verification

VKAT can manually be used with the "verify" sub command in order to (re-)verify previously generated test sets. It then will return different exit codes based on the verification result.

Performing an automated test

• TxS (Test E[x]ecution Service) has to be up and running (part of the Validation Kit) on the guest.
• Invoke the tdAudioTest.py test driver, either manually or fully automated via Test Manager.

Troubleshooting

• Make sure that audio device emulation is enabled and can be used within the guest. Also, audio input / output has to be enabled, depending on the tests.
• Make sure that the guest's VKAT instance can reach the host via the selected transport lay (TCP/IP by default).
• Increase the hosts audio logging level (via extra-data, set "VBoxInternal2/Audio/Debug/Level" to "5").
• Increase VKAT's verbosity level (add "-v", can be specified multiple times).
• Check if the the VBox release log contains any warnings / errors with the "ValKit:" prefix.