Issue #34: Fixed unit test for ticket articles due to ZAA-2020-24.

Author: jepf

README.md

@@ -108,6 +108,8 @@ $ticket->save();
 if ( $ticket->isDirty() ) {...}
 ```
 
+Note: Some resource types don't support updating the values of certain fields. Please refer to the API documentation (see links above).
+
 ### Creating Resource objects
 To create a new `Resource` object, use the following code (example):
 ```php

test/ZammadAPIClient/Resource/TicketArticleTest.php

@@ -7,7 +7,6 @@
 class TicketArticleTest extends AbstractBaseTest
 {
     protected $resource_type = ResourceType::TICKET_ARTICLE;
-    protected $update_field  = 'body';
 
     public function objectCreateProvider()
     {
@@ -185,4 +184,55 @@ public function testCreate( $values, $expected_success )
             );
         }
     }
+
+    /**
+     * @depends testCreate
+     */
+    public function testUpdate()
+    {
+        foreach ( self::$created_objects as $created_object ) {
+            $created_object_id = $created_object->getID();
+            if ( empty( $created_object_id ) ) {
+                continue;
+            }
+
+            // Change a value.
+            $is_internal     = $created_object->getValue('internal') ? true : false;
+            $new_is_internal = !$is_internal;
+
+            $created_object->setValue( 'internal', $new_is_internal );
+            $saved_object = $created_object->save();
+
+            $this->assertFalse(
+                $created_object->hasError(),
+                'Error must not be set after update of object.'
+            );
+
+            $this->assertInstanceOf(
+                $this->resource_type,
+                $saved_object
+            );
+
+            $this->assertSame(
+                $created_object,
+                $saved_object,
+                'Saving an object must return the same object again.'
+            );
+
+            // Compare changed value.
+            $this->assertEquals(
+                $new_is_internal,
+                $created_object->getValue('internal') ? true : false,
+                'Changed value of object must match expected one.'
+            );
+
+            // Fetch object data with a fresh object to check again if value has been changed.
+            $fetched_object = self::getClient()->resource( $this->resource_type )->get($created_object_id);
+            $this->assertEquals(
+                $new_is_internal,
+                $fetched_object->getValue('internal') ? true : false,
+                'Value of fetched object must match expected one.'
+            );
+        }
+    }
 }