Added message string representation

Author: repejota

tests/Unit/MessageTest.php

@@ -25,14 +25,26 @@ public function testSettersAndGetters()
         $this->assertEquals('sid', $msg->getSid());
         $this->assertEquals($conn, $msg->getConn());
 
-        $msg
-            ->setSubject('subject2')
+        $msg->setSubject('subject2')
             ->setBody('body2')
             ->setSid('sid2');
 
         $this->assertEquals('subject2', $msg->getSubject());
         $this->assertEquals('body2', $msg->getBody());
         $this->assertEquals('sid2', $msg->getSid());
+    }
+
+    /**
+     * Tests Message string representation.
+     *
+     * @return void
+     */
+    public function testMessageStringRepresentation()
+    {
+        $conn = new Connection();
+
+        $msg = new Message('subject', 'body', 'sid', $conn);
 
+        $this->assertEquals('body', $msg->__toString());
     }
 }