diff --git a/src/Core/ServiceBuilder.php b/src/Core/ServiceBuilder.php
index 05d5641abe52..653e055a0e99 100644
--- a/src/Core/ServiceBuilder.php
+++ b/src/Core/ServiceBuilder.php
@@ -118,7 +118,7 @@ public function __construct(array $config = [])
      */
     public function bigQuery(array $config = [])
     {
-        return new BigQueryClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(BigQueryClient::class, 'bigquery', $config);
     }
 
     /**
@@ -142,7 +142,7 @@ public function bigQuery(array $config = [])
      */
     public function datastore(array $config = [])
     {
-        return new DatastoreClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(DatastoreClient::class, 'datastore', $config);
     }
 
     /**
@@ -162,7 +162,7 @@ public function datastore(array $config = [])
      */
     public function logging(array $config = [])
     {
-        return new LoggingClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(LoggingClient::class, 'logging', $config);
     }
 
     /**
@@ -183,7 +183,7 @@ public function logging(array $config = [])
      */
     public function language(array $config = [])
     {
-        return new LanguageClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(LanguageClient::class, 'language', $config);
     }
 
     /**
@@ -207,7 +207,7 @@ public function language(array $config = [])
      */
     public function pubsub(array $config = [])
     {
-        return new PubSubClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(PubSubClient::class, 'pubsub', $config);
     }
 
     /**
@@ -232,7 +232,7 @@ public function pubsub(array $config = [])
      */
     public function spanner(array $config = [])
     {
-        return new SpannerClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(SpannerClient::class, 'spanner', $config);
     }
 
     /**
@@ -261,7 +261,7 @@ public function spanner(array $config = [])
      */
     public function speech(array $config = [])
     {
-        return new SpeechClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(SpeechClient::class, 'speech', $config);
     }
 
     /**
@@ -280,7 +280,7 @@ public function speech(array $config = [])
      */
     public function storage(array $config = [])
     {
-        return new StorageClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(StorageClient::class, 'storage', $config);
     }
 
 
@@ -300,7 +300,7 @@ public function storage(array $config = [])
      */
     public function trace(array $config = [])
     {
-        return new TraceClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(TraceClient::class, 'trace', $config);
     }
 
     /**
@@ -320,7 +320,7 @@ public function trace(array $config = [])
      */
     public function vision(array $config = [])
     {
-        return new VisionClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(VisionClient::class, 'vision', $config);
     }
 
     /**
@@ -368,7 +368,18 @@ public function vision(array $config = [])
      */
     public function translate(array $config = [])
     {
-        return new TranslateClient($config ? $this->resolveConfig($config) : $this->config);
+        return $this->createClient(TranslateClient::class, 'translate', $config);
+    }
+
+    private function createClient($class, $packageName, array $config = [])
+    {
+        if (class_exists($class)) {
+            return new $class($config ? $this->resolveConfig($config) : $this->config);
+        }
+        throw new \Exception(sprintf(
+            'The google/cloud-%s package is missing and must be installed.',
+            $packageName
+        ));
     }
 
     /**
diff --git a/tests/system/Core/ServicesNotFoundTest.php b/tests/unit/Core/ServicesNotFoundTest.php
similarity index 65%
rename from tests/system/Core/ServicesNotFoundTest.php
rename to tests/unit/Core/ServicesNotFoundTest.php
index 7623c2d5632a..017b63175ac3 100644
--- a/tests/system/Core/ServicesNotFoundTest.php
+++ b/tests/unit/Core/ServicesNotFoundTest.php
@@ -15,32 +15,37 @@
  * limitations under the License.
  */
 
-namespace Google\Cloud\Tests\System\Core;
+namespace Google\Cloud\Tests\Unit\Core;
 
 use Google\Cloud\Core\ServiceBuilder;
+use Composer\Autoload\ClassLoader;
 
 /**
  * @group core
  */
 class ServicesNotFoundTest extends \PHPUnit_Framework_TestCase
 {
-    private static $autoloaders;
+    private static $previousAutoloadFunc;
+    private static $newAutoloadFunc;
     private static $cloud;
 
     public static function setUpBeforeClass()
     {
         self::$cloud = new ServiceBuilder;
-        self::$autoloaders = spl_autoload_functions();
-        foreach (self::$autoloaders as $function) {
-            spl_autoload_unregister($function);
+        foreach (spl_autoload_functions() as $function) {
+            if ($function[0] instanceof ClassLoader) {
+                $newAutoloader = clone $function[0];
+                $newAutoloader->setPsr4('Google\Cloud\\', '/tmp');
+                spl_autoload_register(self::$newAutoloadFunc = [$newAutoloader, 'loadClass']);
+                spl_autoload_unregister(self::$previousAutoloadFunc = $function);
+            }
         }
     }
 
     public static function tearDownAfterClass()
     {
-        foreach (self::$autoloaders as $function) {
-            spl_autoload_register($function);
-        }
+        spl_autoload_register(self::$previousAutoloadFunc);
+        spl_autoload_unregister(self::$newAutoloadFunc);
     }
 
     public function serviceBuilderMethods()
@@ -61,11 +66,13 @@ public function serviceBuilderMethods()
     }
 
     /**
+     * @runInSeparateProcess
+     * @preserveGlobalState disabled
      * @dataProvider serviceBuilderMethods
      */
     public function testServicesNotFound($method)
     {
-        $this->setExpectedException('Exception', sprintf(
+        $this->setExpectedException(\Exception::class, sprintf(
             'The google/cloud-%s package is missing and must be installed.',
             strtolower($method)
         ));