Attempt fixing usage of InstalledVersions in tests

tests/Composer/Test/InstalledVersionsTest.php

@@ -17,6 +17,8 @@ use Composer\Semver\VersionParser;
 
 class InstalledVersionsTest extends TestCase
 {
+    private static $previousRegisteredLoaders;
+
     /**
      * @var string
      */
@@ -28,12 +30,16 @@ class InstalledVersionsTest extends TestCase
         // class loaders are registered
         $prop = new \ReflectionProperty('Composer\Autoload\ClassLoader', 'registeredLoaders');
         $prop->setAccessible(true);
+        self::$previousRegisteredLoaders = $prop->getValue();
         $prop->setValue(array());
     }
 
     public static function tearDownAfterClass()
     {
-        self::setUpBeforeClass();
+        $prop = new \ReflectionProperty('Composer\Autoload\ClassLoader', 'registeredLoaders');
+        $prop->setAccessible(true);
+        $prop->setValue(self::$previousRegisteredLoaders);
+        InstalledVersions::reload(null); // @phpstan-ignore-line
     }
 
     public function setUp()