phpunit, laravel: Cannot use "parent" when current class scope has no parent

I had same issue - it turned out that mockery/mockery was set to version 0.9 in my composer.json. Upgrading mockery/mockery to version 1.3 solved the problem for me.

Related composer.json fragment:

        "mockery/mockery": "~1.3.0",
        "phpunit/phpunit": "~8.0",

Try setting same versions and run composer update