add exception management, correct mistakes in error management in Image.php and add function to simplify parameters using in tests

server/Test/AppTestClass.php

@@ -89,10 +89,16 @@ class AppTest{
 	}
 	
 	public function getPostParam($name){
-		
+
 		return $this->postParams[$name];
 		
 	}
+
+	public function setPostParam($name, $value){
+		
+		$this->postParams[$name] = $value;
+
+	}
 	
 	public function setOutput($key, $out){