If you are running with an artifact build locally, the geckodriver binary will never be build. As such you have to download it yourself via github's releases page, or build via `cargo build` inside of `testing/geckodriver`. For users who just want to have an executable the `mach artifact` command would be perfect to let them download a version of geckodriver. And that maybe even not only a release version but also a build as created from the current changeset on mozilla-central.

For the per commit build we would need compiled builds across all platforms. It means it depends on bug 1417646.

This actually works now because the binary is build on all platforms, and as such downloaded with the common tests package when running a `mach build` for an artifact build locally. Running the wdspec tests will find the downloaded binary and use it: > 0:46.70 pid:20322 Full command: /Volumes/data/code/gecko/obj/debug/dist/NightlyDebug.app/Contents/MacOS/geckodriver --marionette-port 2828 --host 127.0.0.1 --port 4444 So this is fixed by bug 1417649.