fix test and README

Author: actionm

README.md

@@ -239,7 +239,7 @@ $client = new Client(
 ```
 
 
-The Client constructor also receives an optional "httpOptions" array, which can be used to add custom [Guzzle HTTP Client request options](https://guzzle.readthedocs.io/en/latest/request-options.html).
+The Client constructor also receives an optional "httpOptions" array, which **overrides** the "authorizationHeaders" and can be used to add custom [Guzzle HTTP Client request options](https://guzzle.readthedocs.io/en/latest/request-options.html).
 
 Example:
 

tests/ClientTest.php

@@ -89,14 +89,12 @@ public function testConstructClient()
         $secondRequest = $container[2]['request'];
         $this->assertEquals('{"query":"query_string","variables":{"name":"val"}}', $secondRequest->getBody()->getContents());
 
-
         /** @var Request $fourthRequest */
         $fourthRequest = $container[3]['request'];
-        $this->assertNotNull($fourthRequest->getHeader('Authorization'));
+        $this->assertNotEmpty($fourthRequest->getHeader('Authorization'));
         $this->assertNotEmpty($fourthRequest->getHeader('User-Agent'));
         $this->assertEquals(['Basic zyx'], $fourthRequest->getHeader('Authorization'));
         $this->assertEquals(['test'], $fourthRequest->getHeader('User-Agent'));
-
     }
 
     /**