Updated test cases documentation

docs/test_cases/t20017.md

@@ -21,6 +21,16 @@ diagrams:
       - function: "clanguml::t20017::tmain()"
 ```
 ## Source code
+File t20017_b.cc
+```cpp
+#include "include/t20017_b.h"
+
+namespace clanguml {
+namespace t20017 {
+int b1(int x, int y) { return x - y; }
+}
+}
+```
 File t20017.cc
 ```cpp
 #include "include/t20017_a.h"
@@ -32,15 +42,5 @@ int tmain() { return b2(a1(a2(a3(1, 2), b1(3, 4)), 5), 6); }
 }
 }
 ```
-File t20017_b.cc
-```cpp
-#include "include/t20017_b.h"
-
-namespace clanguml {
-namespace t20017 {
-int b1(int x, int y) { return x - y; }
-}
-}
-```
 ## Generated UML diagrams
 ![t20017_sequence](./t20017_sequence.svg "Test case for combine_free_functions_into_file_participants option")