Added abstract factory pattern

docs/test_cases.md

@@ -18,6 +18,7 @@
  * [t00017](./test_cases/t00017.md) - Test include relations also as members flag
  * [t00018](./test_cases/t00018.md) - Pimpl pattern
  * [t00019](./test_cases/t00019.md) - Layercake pattern
+ * [t00020](./test_cases/t00020.md) - Abstract factory pattern
 ## Sequence diagrams
  * [t20001](./test_cases/t20001.md) - Basic sequence diagram
 ## Configuration diagrams

docs/test_cases/t00019.md

@@ -73,8 +73,8 @@ File t00019_layer1.h
 ```cpp
 #pragma once
 
-#include <string>
 #include <iostream>
+#include <string>
 
 namespace clanguml {
 namespace t00019 {