None of the tests modify the data, so there's no risk that one test
will cause another to fail via that. We can thus avoid the repeated
cost of that set-up and teardown, which was done repeatedly for each
test function since benchmarks get run repeatedly if they're quick.
Use QTemporaryDir to manage the test data, so that it's tidied away
automagically, instead of trying to tidy up at the end of each test
(which was, of course, skipped if the test failed).
As drive-bys, fix a typo in a QFAIL()'s message, change some C casts
that silently bulldozed const away to reinterpret_cast<>s with the
const qualifier and turn some heap buffers into stack buffers to save
the need to delete [] them at the end of their tests (also skipped on
failure).
Inspired by a kindred change by Andreas Buhr and a suggestion on its
review by Friedemann Kleint.
Pick-to: 6.2 6.1 5.15
Change-Id: I6067eb35babfbac02990ef39817b0d5122f563cd
Reviewed-by: Andreas Buhr <andreas.buhr@qt.io>
e1b3a46302