Find not a test with valid phpunit suffix

find_not_tests.php

<?php

require_once __DIR__.'/../src/test/bootstrap.php';

$finder = new \Symfony\Component\Finder\Finder();
$finder->in(__DIR__.'/../src')
    ->name('*Test.php')
    ->files();

foreach($finder as $file) {
    /** @var \Symfony\Component\Finder\SplFileInfo $file */
    if (!isTest($file->getPathname())) {
        echo $file->getPathname().PHP_EOL;
    }
}

function isTest($filename)
{
    $ref = new \Go\ParserReflection\ReflectionFile($filename);
    foreach ($ref->getFileNamespaces() as $namespace) {
        foreach ($namespace->getClasses() as $class) {
            require_once $filename;
            return $class->isSubclassOf(\PHPUnit_Framework_TestCase::class);
        }
    }
}