Depracted warning CakePHP 3, PHPUnit 6, PHP 7.4

Deprecated Error: Function ReflectionType::__toString() is deprecated in […/vendor/phpunit/phpunit-mock-objects/src/Generator.php, line 919]

See also https://github.com/sebastianbergmann/phpunit/issues/3728

Has someone found a good solution/workaround if you only need to support PHP 7.2+?