fix regression sebastianbergmann#3889

src/Runner/StandardTestSuiteLoader.php

@@ -9,6 +9,7 @@
  */
 namespace PHPUnit\Runner;
 
+use PHPUnit\Framework\TestCase;
 use PHPUnit\Util\FileLoader;
 use PHPUnit\Util\Filesystem;
 use ReflectionClass;
@@ -62,6 +63,12 @@ public function load(string $suiteClassName, string $suiteClassFile = ''): Refle
 
                 break;
             }
+
+            if ($class->isSubclassOf(TestCase::class)) {
+                $suiteClassName = $loadedClass;
+
+                break;
+            }
         }
 
         if (!\class_exists($suiteClassName, false) ||

tests/end-to-end/regression/GitHub/3889-2.phpt

@@ -0,0 +1,18 @@
+--TEST--
+https://github.com/sebastianbergmann/phpunit/issues/3889
+--FILE--
+<?php declare(strict_types=1);
+$_SERVER['argv'][1] = '--no-configuration';
+$_SERVER['argv'][4] = __DIR__ . '/3889/MyIssue3889Test.php';
+
+require __DIR__ . '/../../../bootstrap.php';
+
+PHPUnit\TextUI\Command::main();
+--EXPECTF--
+PHPUnit %s by Sebastian Bergmann and contributors.
+
+.                                                                   1 / 1 (100%)
+
+Time: %s, Memory: %s
+
+OK (1 test, 1 assertion)

tests/end-to-end/regression/GitHub/3889.phpt

@@ -0,0 +1,20 @@
+--TEST--
+https://github.com/sebastianbergmann/phpunit/issues/3889
+--FILE--
+<?php declare(strict_types=1);
+$_SERVER['argv'][1] = '--no-configuration';
+$_SERVER['argv'][2] = '--test-suffix';
+$_SERVER['argv'][3] = '.test.php';
+$_SERVER['argv'][4] = __DIR__ . '/3889/Issue3889Test.test.php';
+
+require __DIR__ . '/../../../bootstrap.php';
+
+PHPUnit\TextUI\Command::main();
+--EXPECTF--
+PHPUnit %s by Sebastian Bergmann and contributors.
+
+.                                                                   1 / 1 (100%)
+
+Time: %s, Memory: %s
+
+OK (1 test, 1 assertion)

tests/end-to-end/regression/GitHub/3889/Issue3889Test.test.php

@@ -0,0 +1,18 @@
+<?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.
+ */
+use PHPUnit\Framework\TestCase;
+
+final class Issue3889Test extends TestCase
+{
+    public function testOne(): void
+    {
+        $this->assertTrue(true);
+    }
+}

tests/end-to-end/regression/GitHub/3889/MyIssue3889Test.php

@@ -0,0 +1,18 @@
+<?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.
+ */
+use PHPUnit\Framework\TestCase;
+
+final class Issue3889Test extends TestCase
+{
+    public function testOne(): void
+    {
+        $this->assertTrue(true);
+    }
+}