diff --git a/cmd/codegen/testdata/Makefile b/cmd/codegen/testdata/Makefile
new file mode 100644
index 00000000..5506544b
--- /dev/null
+++ b/cmd/codegen/testdata/Makefile
@@ -0,0 +1,4 @@
+all:
+	mkdir -p output
+	cd output; \
+		go run ../.. --verbose --package mypkg --include header.h --preset ..//preset.json -lng -lg -d ../deffinitions.json -e ../structs_and_enums.json -t ../typedefs_dict.json
diff --git a/cmd/codegen/testdata/deffinitions.json b/cmd/codegen/testdata/deffinitions.json
new file mode 100644
index 00000000..9f418590
--- /dev/null
+++ b/cmd/codegen/testdata/deffinitions.json
@@ -0,0 +1,21 @@
+{
+    "FuncName": {
+        "ov_cimguiname": "Foo",
+        "original_func_name": "OrgFoo",
+        "args": "(A a)",
+        "argsT": [
+            {
+                "name": "a",
+                "type": "A",
+                "custom_type": ""
+            }
+        ],
+        "defaults": {
+            "a": "1"
+        },
+        "nonUDT": 0,
+        "comment": "function comment (optional)",
+        "location": 15
+    }
+}
+
diff --git a/cmd/codegen/testdata/output/callbacks.go b/cmd/codegen/testdata/output/callbacks.go
new file mode 100644
index 00000000..21031669
--- /dev/null
+++ b/cmd/codegen/testdata/output/callbacks.go
@@ -0,0 +1,11 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+package mypkg
+
+// #include <stdlib.h>
+// #include <memory.h>
+// #include "wrapper.h"
+// #include "typedefs.h"
+
+import "C"
diff --git a/cmd/codegen/testdata/output/enums.go b/cmd/codegen/testdata/output/enums.go
new file mode 100644
index 00000000..0b88b123
--- /dev/null
+++ b/cmd/codegen/testdata/output/enums.go
@@ -0,0 +1,14 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+package mypkg
+
+// this is an example enum
+// original name: A_
+type A int32
+
+const (
+	// A default value of A
+	ADefault A = 0
+	AOne     A = 1
+)
diff --git a/cmd/codegen/testdata/output/funcs.go b/cmd/codegen/testdata/output/funcs.go
new file mode 100644
index 00000000..fdadb4b2
--- /dev/null
+++ b/cmd/codegen/testdata/output/funcs.go
@@ -0,0 +1,39 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+package mypkg
+
+// #include "structs_accessor.h"
+// #include "wrapper.h"
+
+import "C"
+
+func (self B) SetField1(v int32) {
+	selfArg, selfFin := self.Handle()
+	defer selfFin()
+	C.wrap_B_SetField1(selfArg, C.int(v))
+}
+
+func (self *B) Field1() int32 {
+	selfArg, selfFin := self.Handle()
+
+	defer func() {
+		selfFin()
+	}()
+	return int32(C.wrap_B_GetField1(internal.ReinterpretCast[*C.B](selfArg)))
+}
+
+func (self B) SetField2(v A) {
+	selfArg, selfFin := self.Handle()
+	defer selfFin()
+	C.wrap_B_SetField2(selfArg, C.A(v))
+}
+
+func (self *B) Field2() A {
+	selfArg, selfFin := self.Handle()
+
+	defer func() {
+		selfFin()
+	}()
+	return A(C.wrap_B_GetField2(internal.ReinterpretCast[*C.B](selfArg)))
+}
diff --git a/cmd/codegen/testdata/output/structs_accessor.cpp b/cmd/codegen/testdata/output/structs_accessor.cpp
new file mode 100644
index 00000000..9c7d16f4
--- /dev/null
+++ b/cmd/codegen/testdata/output/structs_accessor.cpp
@@ -0,0 +1,12 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+
+#include <string.h>
+#include "wrapper.h"
+#include "structs_accessor.h"
+
+void wrap_B_SetField1(B *BPtr, int v) { BPtr->Field1 = v; }
+int wrap_B_GetField1(B *self) { return self->Field1; }
+void wrap_B_SetField2(B *BPtr, A v) { BPtr->Field2 = v; }
+A wrap_B_GetField2(B *self) { return self->Field2; }
diff --git a/cmd/codegen/testdata/output/structs_accessor.h b/cmd/codegen/testdata/output/structs_accessor.h
new file mode 100644
index 00000000..3f263c0c
--- /dev/null
+++ b/cmd/codegen/testdata/output/structs_accessor.h
@@ -0,0 +1,19 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+#pragma once
+
+#include "wrapper.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern void wrap_B_SetField1(B *BPtr, int v);
+extern int wrap_B_GetField1(B *self);
+extern void wrap_B_SetField2(B *BPtr, A v);
+extern A wrap_B_GetField2(B *self);
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/cmd/codegen/testdata/output/typedefs.cpp b/cmd/codegen/testdata/output/typedefs.cpp
new file mode 100644
index 00000000..c84473a3
--- /dev/null
+++ b/cmd/codegen/testdata/output/typedefs.cpp
@@ -0,0 +1,6 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+
+#include "typedefs.h"
+#include "header.h"
diff --git a/cmd/codegen/testdata/output/typedefs.go b/cmd/codegen/testdata/output/typedefs.go
new file mode 100644
index 00000000..1170dd9b
--- /dev/null
+++ b/cmd/codegen/testdata/output/typedefs.go
@@ -0,0 +1,37 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+package mypkg
+
+// #include <stdlib.h>
+// #include <memory.h>
+// #include "wrapper.h"
+// #include "typedefs.h"
+
+import "C"
+
+type B struct {
+	CData *C.B
+}
+
+// Handle returns C version of B and its finalizer func.
+func (self *B) Handle() (result *C.B, fin func()) {
+	return self.CData, func() {}
+}
+
+// C is like Handle but returns plain type instead of pointer.
+func (self B) C() (C.B, func()) {
+	result, fn := self.Handle()
+	return *result, fn
+}
+
+// NewEmptyB creates B with its 0 value.
+func NewEmptyB() *B {
+	return &B{CData: new(C.B)}
+}
+
+// NewBFromC creates B from its C pointer.
+// SRC ~= *C.B
+func NewBFromC[SRC any](cvalue SRC) *B {
+	return &B{CData: internal.ReinterpretCast[*C.B](cvalue)}
+}
diff --git a/cmd/codegen/testdata/output/typedefs.h b/cmd/codegen/testdata/output/typedefs.h
new file mode 100644
index 00000000..24b6730a
--- /dev/null
+++ b/cmd/codegen/testdata/output/typedefs.h
@@ -0,0 +1,15 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+
+#pragma once
+
+#include "header.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef __cplusplus
+}
+#endif
\ No newline at end of file
diff --git a/cmd/codegen/testdata/output/wrapper.cpp b/cmd/codegen/testdata/output/wrapper.cpp
new file mode 100644
index 00000000..836615cf
--- /dev/null
+++ b/cmd/codegen/testdata/output/wrapper.cpp
@@ -0,0 +1,6 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+#include "wrapper.h"
+#include "header.h"
+
diff --git a/cmd/codegen/testdata/output/wrapper.h b/cmd/codegen/testdata/output/wrapper.h
new file mode 100644
index 00000000..f3f1a260
--- /dev/null
+++ b/cmd/codegen/testdata/output/wrapper.h
@@ -0,0 +1,15 @@
+// Code generated by cmd/codegen from https://github.com/AllenDang/cimgui-go.
+// DO NOT EDIT.
+
+#pragma once
+
+#include "header.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/cmd/codegen/testdata/preset.json b/cmd/codegen/testdata/preset.json
new file mode 100644
index 00000000..db57a49c
--- /dev/null
+++ b/cmd/codegen/testdata/preset.json
@@ -0,0 +1,13 @@
+{
+        "PackagePath": "example.com/mypkg",
+        "TypedefsPoolSize": 32,
+        "DefaultArgReplace": {
+                "nullptr":    "0",
+                "NULL":       "0",
+                "((void*)0)": "0"
+        },
+        "DefaultArgArbitraryValue": {
+                "text_end":  "0",
+                "text_end_": "0"
+        }
+}
diff --git a/cmd/codegen/testdata/structs_and_enums.json b/cmd/codegen/testdata/structs_and_enums.json
new file mode 100644
index 00000000..46b025ad
--- /dev/null
+++ b/cmd/codegen/testdata/structs_and_enums.json
@@ -0,0 +1,39 @@
+{
+        "structs":{
+                "B":[
+                        {
+                                "name": "Field1",
+                                "type": "int"
+                        },
+                        {
+                                "name": "Field2",
+                                "type": "A"
+                        }
+                ]
+        },
+        "struct_comments": {
+                "B": {
+                        "above": "// this is an example struct"
+                }
+        },
+        "enums": {
+                "A_": [
+                        {
+                                "calc_value": 0,
+                                "comment": "// A default value of A",
+                                "name": "A_Default",
+                                "value": "0"
+                        },
+                        {
+                                "calc_value": 1,
+                                "name": "A_One",
+                                "value": "1 << 0"
+                        }
+                ]
+        },
+        "enum_comments": {
+                "A_": {
+                        "above": "// this is an example enum"
+                }
+        }
+}
diff --git a/cmd/codegen/testdata/typedefs_dict.json b/cmd/codegen/testdata/typedefs_dict.json
new file mode 100644
index 00000000..01008955
--- /dev/null
+++ b/cmd/codegen/testdata/typedefs_dict.json
@@ -0,0 +1,4 @@
+{
+        "A": "int",
+        "B": "struct B"
+}