vuinputd/docs/TESTS.md

Tests

Integration tests

Ensure, you have a /run/vuinputd/vuinput-test-folder that allows the usage of character devices:

mkdir -p /run/vuinputd/vuinput-test
mount -t tmpfs -o mode=755,size=1M tmpfs /run/vuinputd/vuinput-test
mkdir -p /run/vuinputd/vuinput-test/dev
mkdir -p /run/vuinputd/vuinput-test/dev-input
mkdir -p /run/vuinputd/vuinput-test/udev

With bubblewrap

Install bubblewrap: apt-get install bubblewrap.

Run with cargo test -p vuinputd-tests --features "requires-privileges requires-uinput requires-bwrap" -- --test-threads=1.

With podman

Install podman: apt-get install podman.

Create test container for podman

cargo build -p vuinputd-tests
podman build --dns 1.1.1.1 -t vuinputd-tests -f vuinputd-tests/podman/Containerfile .

Run with cargo test -p vuinputd-tests --features "requires-privileges requires-uinput requires-podman" -- --test-threads=1.

Performance tests

Using CUSE introduces an additional round trip between kernel and userspace, which inevitably adds overhead compared to direct uinput access. To estimate the order of magnitude of this overhead, the vuinputd-tests include a simple integration test that emits two input events: once using direct uinput access and once via vuinputd v0.3.

The test measures the elapsed time between emitting an event and receiving it again, using CLOCK_MONOTONIC. The measured latencies were:

• First call: 16 µs (direct uinput) vs. 90 µs (vuinputd)
• Second call: 7 µs (direct uinput) vs. 68 µs (vuinputd)

As expected, vuinputd introduces a clearly measurable performance penalty due to the additional userspace round trip. However, even in this best-case microbenchmark, the absolute overhead remains well below 0.1 ms per event.

In practical terms, this level of overhead is negligible for real-world usage. For latency-sensitive applications such as gaming, tens of microseconds are several orders of magnitude smaller than typical sources of latency such as frame rendering time, compositor delays, scheduling jitter, or network latency. Even a single rendered frame at 60 Hz already accounts for roughly 16.6 ms, making the additional cost introduced by vuinputd effectively unobservable to the user.

It is important to note that this benchmark is intentionally minimal and primarily intended to provide a rough sense of scale. It does not model realistic workloads, higher event rates, or concurrent inputs. More comprehensive benchmarks are required to assess behavior under load and contention. Nevertheless, these results demonstrate that the architectural approach taken by vuinputd is sound and does not introduce prohibitive latency by design. As long as more realistic benchmarks confirm similar behavior under load, vuinputd can be considered suitable even for interactive and latency-sensitive use cases.

Detailed results:

integration_tests.rs#test_keyboard_in_container_with_uinput:

{"events":[{"tv_sec":3133476,"tv_nsec":947503794,"duration_usec":16,"type_":1,"code":57,"value":1,"send_and_receive_match":true},{"tv_sec":3133476,"tv_nsec":947520555,"duration_usec":7,"type_":1,"code":57,"value":0,"send_and_receive_match":true}]}

integration_tests.rs#test_keyboard_in_container_with_vuinput:

Event log: {"events":[{"tv_sec":3133303,"tv_nsec":796108454,"duration_usec":90,"type_":1,"code":57,"value":1,"send_and_receive_match":true},{"tv_sec":3133303,"tv_nsec":796198973,"duration_usec":68,"type_":1,"code":57,"value":0,"send_and_receive_match":true}]}

Manual end-to-end tests

vuinputd	host	input type	app that creates device	app that reads device	working	Notes
0.2.0	Ubuntu 24.04 amd64	virtual keyboard	Sunshine (via moonlight-qt 6.1.0 on macos)	labwc via libinput	✅	(1)
0.2.0	Ubuntu 24.04 amd64	virtual mouse	Sunshine (via moonlight-qt 6.1.0 on macos)	labwc via libinput	✅)	(1)
0.2.0	Ubuntu 24.04 amd64	virtual keyboard	Steam (via Remote Play from Mac)	Return to Monkey Island	✅	(2)
0.2.0	Ubuntu 24.04 amd64	virtual gamepad	Steam (via Remote Play from Mac)	Return to Monkey Island	❌	(2)

(1) works also for programs running on the wayland desktop
(2) Steam is a 32-bit application on linux