Create test bootstrap for autoloading

phpunit.xml.dist

@@ -11,7 +11,7 @@
          convertWarningsToExceptions="true"
          stopOnFailure="false"
          syntaxCheck="false"
-         bootstrap="vendor/autoload.php"
+         bootstrap="tests/bootstrap.php"
 >
 
     <php>

tests/bootstrap.php

+<?php
+
+if (file_exists(__DIR__ . '/../vendor/autoload.php')) {
+    // Dependencies were installed with Composer and this is the main project
+    $loader = require_once __DIR__ . '/../vendor/autoload.php';
+} elseif (file_exists(__DIR__ . '/../../../../autoload.php')) {
+    // We're installed as a dependency in another project's `vendor` directory
+    $loader = require_once __DIR__ . '/../../../../autoload.php';
+} else {
+    throw new Exception('Can\'t find autoload.php. Did you install dependencies with Composer?');
+}
+
+$loader->addPsr4('MongoDB\\Tests\\', __DIR__);