Add tests

tests/_files/NoTestCase.php

@@ -0,0 +1,14 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace PHPUnit\TestFixture;
+
+final class NoTestCase
+{
+}

tests/unit/Framework/TestSuiteTest.php

@@ -11,10 +11,12 @@
 
 use PHPUnit\Framework\Attributes\CoversClass;
 use PHPUnit\Framework\Attributes\Small;
+use PHPUnit\TestFixture\AbstractTestCase;
 use PHPUnit\TestFixture\DependencyFailureTest;
 use PHPUnit\TestFixture\DependencyOnClassTest;
 use PHPUnit\TestFixture\DependencySuccessTest;
 use PHPUnit\TestFixture\MultiDependencyTest;
+use PHPUnit\TestFixture\NoTestCase;
 use PHPUnit\TestFixture\NotPublicTestCase;
 use ReflectionClass;
 
@@ -111,4 +113,22 @@ public function testResolverOnlyUsesSuitesAndCases(): void
             DependencyFailureTest::class . '::class',
         ], $suite->requires(), 'Required test names incorrect');
     }
+
+    public function testRejectsAbstractTestClass(): void
+    {
+        $suite = TestSuite::empty('the-test-suite');
+
+        $this->expectException(Exception::class);
+
+        $suite->addTestSuite(new ReflectionClass(AbstractTestCase::class));
+    }
+
+    public function testRejectsClassThatDoesNotExtendTestClass(): void
+    {
+        $suite = TestSuite::empty('the-test-suite');
+
+        $this->expectException(Exception::class);
+
+        $suite->addTestSuite(new ReflectionClass(NoTestCase::class));
+    }
 }