diff --git a/gen/data/input/test_data/structs.h b/gen/data/input/test_data/structs.h
index 29c792d..83c67d5 100644
--- a/gen/data/input/test_data/structs.h
+++ b/gen/data/input/test_data/structs.h
@@ -1,45 +1,119 @@
 #ifndef STRUCTS_H
 #define STRUCTS_H
 
-// incomplete type
-// type: _incomplete_struct
-struct _incomplete_struct;
+// Theory
+// ======
+// P = Primitive Type
+// S = Struct
+// E = Enum
+// A = Alias
+// N = Nested (Structs only, cant be aliased)
+// H = Hosting (Structs only, containing the nested struct, cant be primitive)
+// T = typedef
+
+// Structs
+// -------
+// For structs, a combination is needed to define the type of struct
+// S    = Struct (Empty or incomplete, neither primitive nor complex)
+// PS   = Primitive struct (struct containing only primitive types)
+// CS   = Complex struct (struct containing other structs and primitive)
+// NPS  = Nested primitive struct
+
+// Alias vs. Typedef
+// -----------------
+// aliased means direct typedef directly, like
+/*
+ * typedef struct _X {
+     int x;
+ * } X;
+ *
+ */
+
+// Typedef means, not typdeffed directly, but anywhere, like
+// typedef _X X;
+
+
+// Covered combinations
+// ====================
+//
+// (alias) primitive
+// =================
+// _P   = primitive type without a an alias
+// P    = primitive type
+// AP   = Alias of primitive type
+//
+// (aliased) struct [ primitive | complex ]
+// ========================================
+// _PS  = primitive struct without a an alias
+// PS   = primitive struct
+// APS  = Alias of primitive struct
+// _CS  = complex struct without a an alias
+// CS   = complex struct
+// ACS  = alias of a complex struct
+// _CCS = complex complex struct without an alias
+// CCS  = complex complex struct
+// ACCS = alias of a complex complex struct
+//
+// Nested structs
+// ==============
+// there is always a hosting struct and a nesting struct
+// in case of double nesting it can be both
+//
+// simply nested struct [ primitive | complex ]
+// --------------------------------------------
+// (aliased) hosting struct (complex always)
+// _HS   = hosting complex struct without an alias
+// HS    = hosting complex struct
+// AHS   = hosting primitive struct
+// _NPS  = nested primitive struct without an alias
+// _NCS  = nested complex struct without an alias
+//
+// doubly nested struct (complex always)
+// -------------------------------------
+// _HHS  = hosting hosting struct without an alias
+// HHS   = hosting hosting struct
+// AHHS  = alias of a hosting hosting struct
+// _NHS  = nested hosting struct
+// _NNS  = nested nested struct
+
+
+// incomplete type / forward decl
+struct _incomplete_S;
 
 // an empty struct
-// type: _empty_struct
-struct _empty_struct {
+struct _empty_S {
 };
 
-// a struct withouth typdef
-// type: struct _untypedeffed_struct
-struct _untypedeffed_struct {
+struct _PS {
     int x;
     int y;
 };
 
-// a struct containing primititve fields only
-// type: primitive_struct
-typedef struct _primitive_struct {
+typedef struct PS {
     int x;
-    float y;
-    const char* str;
-    char one;
-} primitive_struct;
-
-// a struct that has one typeref
-// type: complex_struct1
-typedef struct _complex_struct1 {
+    int y;
+} APS;
+
+struct _CS {
     int x;
-    primitive_struct p;
-} complex_struct1;
-
-// struct containing typeref to complex_struct1 struct
-// type: _complex_struct2
-struct _complex_struct2 {
-    primitive_struct *p;
-    complex_struct1 *c;
+    APS p;
 };
 
+typedef struct CS {
+    int x;
+    APS p;
+} ACS;
+
+struct _CCS {
+    APS *p;
+    ACS *c;
+};
+
+struct CCS {
+    int p;
+    ACS *c;
+} ACCS;
+
 // nested structs, semantic parent is global
 // type: host2
 typedef struct _host_struct {