Create selser change assignments dynamically. Currently we rely on an external file that needs to be updated manually. The generation is actually already deterministic with a seeded PRNG (seed is the test title), and the overhead of dynamic generation was around 1 second for a full 60-second test run IIRC. So drop the external file and always generate assignments on the fly.
- Speed up selser change assignments. Currently we generate & test for duplicates. We are really generating permutations, which can be done much quicker.
Remember the output of failing (blacklisted) tests and fail if that output changes. We have many tests where our output is actually correct, but due to limitations in the test setup the test is still failing. This can be a difference to the PHP parser output or something like comparing to wt2wt output in selser testing which expects normalization of attribute quoting etc. By failing on changing blacklisted test output we can still catch regressions in our behavior for these tests. We'll also see improvements that are not quite enough to make the tests pass yet. Rewriting the blacklist is easy enough and documents the changes in failing test output along with the commit.