Create a Fallback in the old autoloader for PSR-4 Test\TestCase

lib/autoloader.php

@@ -113,6 +113,10 @@ class Autoloader {
 				// If not found in the root of the app directory, insert '/lib' after app id and try again.
 				$paths[] = $appPath . '/lib/' . strtolower(str_replace('\\', '/', $rest) . '.php');
 			}
+		} elseif ($class === 'Test\\TestCase') {
+			// This File is considered public API, so we make sure that the class
+			// can still be loaded, although the PSR-4 paths have not been loaded.
+			$paths[] = \OC::$SERVERROOT . '/tests/lib/TestCase.php';
 		} elseif (strpos($class, 'Test\\') === 0) {
 			$paths[] = \OC::$SERVERROOT . '/tests/lib/' . strtolower(str_replace('\\', '/', substr($class, 5)) . '.php');
 		}

tests/lib/autoloader.php

@@ -37,6 +37,12 @@ class AutoLoader extends TestCase {
 		], $this->loader->findClass('OC_Files'));
 	}
 
+	public function testLoadTestTestCase() {
+		$this->assertEquals([
+			\OC::$SERVERROOT . '/tests/lib/TestCase.php'
+		], $this->loader->findClass('Test\TestCase'));
+	}
+
 	public function testLoadTestNamespace() {
 		$this->assertEquals([
 			\OC::$SERVERROOT . '/tests/lib/foo/bar.php'