diff --git a/lib/Cake/TestSuite/CakeTestSuiteDispatcher.php b/lib/Cake/TestSuite/CakeTestSuiteDispatcher.php
index 3f470f712..940fef400 100644
--- a/lib/Cake/TestSuite/CakeTestSuiteDispatcher.php
+++ b/lib/Cake/TestSuite/CakeTestSuiteDispatcher.php
@@ -136,9 +136,19 @@ class CakeTestSuiteDispatcher {
 		if (class_exists('PHPUnit_Framework_TestCase')) {
 			return true;
 		}
-		foreach (App::path('vendors') as $vendor) {
+		$phpunitPath = 'phpunit' . DS . 'phpunit';
+		if (defined('PHP_WINDOWS_VERSION_MAJOR')) {
+			$composerGlobalDir[] = env('APPDATA') . DS . 'Composer' . DS . 'vendor' . DS;
+		} else {
+			$composerGlobalDir[] = env('HOME') . DS . '.composer' . DS . 'vendor' . DS;
+		}
+		$vendors = array_merge(App::path('vendors'), $composerGlobalDir);
+		foreach ($vendors as $vendor) {
 			$vendor = rtrim($vendor, DS);
-			if (is_dir($vendor . DS . 'PHPUnit')) {
+			if (is_dir($vendor . DS . $phpunitPath)) {
+				ini_set('include_path', $vendor . DS . $phpunitPath . PATH_SEPARATOR . ini_get('include_path'));
+				break;
+			} elseif (is_dir($vendor . DS . 'PHPUnit')) {
 				ini_set('include_path', $vendor . PATH_SEPARATOR . ini_get('include_path'));
 				break;
 			}