I have a series of test cases that utilize localStorage and cookies for authentication. Right now, with the defaults automatically being applied the lighthouse testing built into WPT is useless since it clears storage by default. This leads to the test de-authing and the lighthouse score being based on an error page. I have worked around this locally by running the node version of lighthouse with cache disabled on the puppeteer instance and the clear storage flag set to false.
It would be great if we could also do something similar on WPT and otherwise specify which tests/options are enabled using the built-in browser version of webpagetest. It would be fantastic if we could track these numbers using the standard testing environment instead of having to caveat locally run test results due to machine differences.