Are you sure they're running the same set of tests? There's over 10000 tests in the full set that webpage runs, but there are subsets and fabrice might be running one of the subsets.
FWIW test262 falls over partway through in Firefox and I have to kill the tab, though it doesn't crash. There are a bunch of test failures as well for things that are probably not implemented by anyone (I'm curious how many of the tests QuickJS actually passes)
My guess for any performance gap would be that the browser runner probably sets up an entirely separate execution context (iframe?) to run each test cleanly so they don't interfere with each other.
To add, QuickJS is almost completely comparable in test coverage, except for internationalization (which makes sense it wasn't a priority, since it's not used in a browser).
FWIW test262 falls over partway through in Firefox and I have to kill the tab, though it doesn't crash. There are a bunch of test failures as well for things that are probably not implemented by anyone (I'm curious how many of the tests QuickJS actually passes)
My guess for any performance gap would be that the browser runner probably sets up an entirely separate execution context (iframe?) to run each test cleanly so they don't interfere with each other.