As can be seen in https://integration.wikimedia.org/ci/job/wmf-quibble-core-vendor-mysql-php72-docker/9691/console :
PHP Fatal error: Declaration of Cache\IntegrationTests\SimpleCacheTest::setUp() must be compatible with PHPUnit\Framework\TestCase::setUp(): void in /workspace/src/vendor/cache/integration-tests/src/SimpleCacheTest.php on line 713
Upstream bug: https://github.com/php-cache/integration-tests/issues/99
The fix appears to be in master, but not released.