@backupStaticProperties and @backupStaticAttributes trigger an error

[sebastianbergmann]

          After upgrading to 10.0.3, using either `@backupStaticProperties` or `@backupStaticAttributes` at the class level triggers this error:

An error occurred inside PHPUnit.

Message:  assert($metadata instanceof BackupStaticProperties)
Location: /var/www/html/framework/vendor/phpunit/phpunit/src/Framework/TestBuilder.php:189

#0 /var/www/html/framework/vendor/phpunit/phpunit/src/Framework/TestBuilder.php(189): assert(false, 'assert($metadat...')
#1 /var/www/html/framework/vendor/phpunit/phpunit/src/Framework/TestBuilder.php(63): PHPUnit\Framework\TestBuilder->backupSettings('ConfigTest', 'testCanSet')
#2 /var/www/html/framework/vendor/phpunit/phpunit/src/Framework/TestSuite.php(491): PHPUnit\Framework\TestBuilder->build(Object(ReflectionClass), 'testCanSet')
#3 /var/www/html/framework/vendor/phpunit/phpunit/src/Framework/TestSuite.php(132): PHPUnit\Framework\TestSuite->addTestMethod(Object(ReflectionClass), Object(ReflectionMethod))
#4 /var/www/html/framework/vendor/phpunit/phpunit/src/Framework/TestSuite.php(229): PHPUnit\Framework\TestSuite::fromClassReflector(Object(ReflectionClass))
#5 /var/www/html/framework/vendor/phpunit/phpunit/src/Framework/TestSuite.php(257): PHPUnit\Framework\TestSuite->addTestSuite(Object(ReflectionClass))
#6 /var/www/html/framework/vendor/phpunit/phpunit/src/Framework/TestSuite.php(275): PHPUnit\Framework\TestSuite->addTestFile('/var/www/html/f...')
#7 /var/www/html/framework/vendor/phpunit/phpunit/src/TextUI/Configuration/TestSuiteBuilder.php(76): PHPUnit\Framework\TestSuite->addTestFiles(Array)
#8 /var/www/html/framework/vendor/phpunit/phpunit/src/TextUI/Configuration/TestSuiteBuilder.php(46): PHPUnit\TextUI\Configuration\TestSuiteBuilder->testSuiteFromPath('/var/www/html/f...', Array)
#9 /var/www/html/framework/vendor/phpunit/phpunit/src/TextUI/Application.php(285): PHPUnit\TextUI\Configuration\TestSuiteBuilder->build(Object(PHPUnit\TextUI\Configuration\Configuration))
#10 /var/www/html/framework/vendor/phpunit/phpunit/src/TextUI/Application.php(97): PHPUnit\TextUI\Application->buildTestSuite(Object(PHPUnit\TextUI\Configuration\Configuration))
#11 /var/www/html/framework/vendor/phpunit/phpunit/phpunit(90): PHPUnit\TextUI\Application->run(Array)
#12 /var/www/html/framework/vendor/bin/phpunit(123): include('/var/www/html/f...')
#13 {main}

It works as expected when added at the method level.

Originally posted by @MichaelRushton in #4603 (comment)