=== Locally ===
If you want to run QR tests locally, you can use <tt>mach</tt> to run them as you would for Gecko normally. Just be sure to set pass <tt>MOZ_WEBRENDER=1--enable-webrender</tt> when running to enable WebRender. On Linux, you should also set the <tt>MOZ_ACCELERATED=1mach</tt> command when running to enable hardware acceleration, without which WebRender will be disabled at runtime. For example, to run the sanity reftests which is a good smoketest that you didn't horribly break everything, you can do this:
MOZ_ACCELERATED=1 MOZ_WEBRENDER=1 ./mach reftest --enable-webrender layout/reftests/reftest-sanity/
You can also run the WR standalone tests (without the Gecko stuff) locally. The page at https://developer.mozilla.org/en-US/docs/Mozilla/QA/WebRender describes how to do this.