Use "autoload-dev" for loading test classes

composer.json

@@ -17,6 +17,9 @@
         "psr-4": { "MongoDB\\": "src/" },
         "files": [ "src/functions.php" ]
     },
+    "autoload-dev": {
+        "psr-4": { "MongoDB\\Tests\\": "tests/" }
+    },
     "extra": {
         "branch-alias": {
             "dev-master": "0.3.x-dev"

tests/bootstrap.php

@@ -9,5 +9,3 @@ if (file_exists(__DIR__ . '/../vendor/autoload.php')) {
 } else {
     throw new Exception('Can\'t find autoload.php. Did you install dependencies with Composer?');
 }
-
-$loader->addPsr4('MongoDB\\Tests\\', __DIR__);