PHPUnit 9 removed what 8 deprecated, on schedule

February brought the removals that 8 had warned about for a year, and a suite that ignored the warnings does not run at all.

$ vendor/bin/phpunit
Call to undefined method TestsOrderTest::assertRegExp()

$ grep -rc 'assertRegExp|assertFileNotExists|assertContains' tests/ 
  | grep -v ':0' | wc -l
188

$ vendor/bin/rector process tests --set phpunit90

Rector handles the mechanical renames reliably, which is most of them. The residue is assertContains, which was split rather than renamed and needs a human to decide per call. Doing the whole thing in one commit with an unchanged assertion count afterwards is the reviewable version — nobody reads 188 files, and equal insertion and deletion counts are the evidence that nothing else changed.