Fix backtrace unit test

.travis.yml

@@ -0,0 +1,14 @@
+language: php
+php:
+  - '5.3'
+  - '5.4'
+  - '5.5'
+  - '5.6'
+  - '7.0'
+  - hhvm
+
+install:
+  - composer --dev install
+
+script:
+  - ./vendor/bin/phpunit

tests/NotifierTest.php

@@ -39,13 +39,14 @@ public function testPostsError()
     public function testPostsBacktrace()
     {
         $backtrace = $this->notifier->notice['errors'][0]['backtrace'];
+        // Note: The following assertion is specific to PHPUnit 4.8.35
         $wanted = array(array(
             'file' => dirname(dirname(__FILE__)) . '/vendor/phpunit/phpunit/src/Framework/TestCase.php',
-            'line' => 742,
+            'line' => 764,
             'function' => 'Airbrake\Tests\NotifyTest->setUp',
         ));
         for ($i = 0; $i < count($wanted); $i++) {
-            $this->assertEquals($backtrace[$i], $wanted[$i]);
+            $this->assertEquals($wanted[$i], $backtrace[$i]);
         }
     }