AddTestsVoidReturnTypeWhereNoReturnRector

Add void to PHPUnit test methods

 use PHPUnit\Framework\TestCase;

 class SomeClass extends TestCase
 {
-    public function testSomething()
+    public function testSomething(): void
     {
     }
 }

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\TypeDeclaration\Rector\Class_\AddTestsVoidReturnTypeWhereNoReturnRector;

return RectorConfig::configure()
    ->withRules([
        AddTestsVoidReturnTypeWhereNoReturnRector::class,
    ]);