revert: inline testing

src/NotExported/MyTestCase.php

@@ -1,18 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Pest\NotExported;
-
-use PHPUnit\Framework\TestCase;
-
-/**
- * @internal
- */
-class MyTestCase extends TestCase // @phpstan-ignore-line
-{
-    public function assertIsTestable(string $testable): void
-    {
-        static::assertSame(MyTestableClass::class, $testable);
-    }
-}

src/NotExported/MyTestableClass.php

@@ -1,22 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Pest\NotExported;
-
-/**
- * @internal
- */
-final class MyTestableClass
-{
-    public function foo(): void
-    {
-        // ...
-    }
-}
-
-it('foo', function () {
-    $testable = new MyTestableClass();
-
-    $this->assertIsTestable(get_class($testable)); // @phpstan-ignore-line
-});