diff -r a10c3e127050 -r bb144d08cd44 test/test_tree.c
--- a/test/test_tree.c	Sun Oct 03 13:07:48 2021 +0200
+++ b/test/test_tree.c	Sun Oct 03 14:06:57 2021 +0200
@@ -60,15 +60,13 @@
     memset(&c, 0, sizeof(TestNode));
     
     // test
-    int ret = cx_tree_add_node(&a, offsetof(TestNode, parent), offsetof(TestNode, prev), offsetof(TestNode, next), &b);
-    CU_ASSERT_EQUAL(ret, 0)
+    cx_tree_add_sibling(&a, offsetof(TestNode, prev), offsetof(TestNode, next), offsetof(TestNode, parent), &b);
     CU_ASSERT_PTR_EQUAL(b.parent, &root)
     CU_ASSERT_PTR_EQUAL(b.prev, &a)
     CU_ASSERT_PTR_NULL(b.next)
     CU_ASSERT_PTR_EQUAL(a.next, &b)
-    
-    ret = cx_tree_add_node(&a, -1, -1, offsetof(TestNode, next), &c);
-    CU_ASSERT_EQUAL(ret, 0)
+
+    cx_tree_add_sibling(&a, -1, offsetof(TestNode, next), -1, &c);
     CU_ASSERT_PTR_NULL(c.parent)
     CU_ASSERT_PTR_NULL(c.prev)
     CU_ASSERT_PTR_NULL(c.next)
@@ -89,63 +87,57 @@
     TestNode a1;
     memset(&a1, 0, sizeof(TestNode));
     
-    int ret;
-    
     // test
-    ret = cx_tree_add_child_node(
-            &root,
-            offsetof(TestNode, parent),
+    cx_tree_add_child(
+            (void **) &root.children_begin,
+            (void **) &root.children_end,
             offsetof(TestNode, prev),
             offsetof(TestNode, next),
-            (void**)&root.children_begin,
-            (void**)&root.children_end,
-            &a);
-    CU_ASSERT_EQUAL(ret, 0)
+            &a,
+            offsetof(TestNode, parent),
+            &root);
     CU_ASSERT_PTR_EQUAL(root.children_begin, &a)
     CU_ASSERT_PTR_EQUAL(root.children_end, &a)
     CU_ASSERT_PTR_EQUAL(a.parent, &root)
     CU_ASSERT_PTR_NULL(a.prev)
     CU_ASSERT_PTR_NULL(a.next)
 
-    ret = cx_tree_add_child_node(
-            &root,
-            offsetof(TestNode, parent),
+    cx_tree_add_child(
+            (void **) &root.children_begin,
+            (void **) &root.children_end,
             offsetof(TestNode, prev),
             offsetof(TestNode, next),
-            (void**)&root.children_begin,
-            (void**)&root.children_end,
-            &b);
-    CU_ASSERT_EQUAL(ret, 0)
+            &b,
+            offsetof(TestNode, parent),
+            &root);
     CU_ASSERT_PTR_NOT_NULL(root.children_begin)
     CU_ASSERT_PTR_EQUAL(root.children_begin->next, &b)
     CU_ASSERT_PTR_EQUAL(root.children_end, &b)
     CU_ASSERT_PTR_EQUAL(b.parent, &root)
     CU_ASSERT_PTR_EQUAL(b.prev, &a)
-    
-    ret = cx_tree_add_child_node(
-            &root,
-            -1,
+
+    cx_tree_add_child(
+            (void **) &root.children_begin,
+            NULL,
             -1,
             offsetof(TestNode, next),
-            (void**)&root.children_begin,
-            NULL,
-            &c);
-    CU_ASSERT_EQUAL(ret, 0)
+            &c,
+            -1,
+            &root);
     CU_ASSERT_PTR_EQUAL(root.children_end, &b) // children_end unchanged
     CU_ASSERT_PTR_EQUAL(b.next, &c)
     CU_ASSERT_PTR_NULL(c.prev)
     CU_ASSERT_PTR_NULL(c.next)
     CU_ASSERT_PTR_NULL(c.parent)
-    
-    ret = cx_tree_add_child_node(
-            &a,
-            offsetof(TestNode, parent),
+
+    cx_tree_add_child(
+            (void **) &a.children_begin,
+            (void **) &a.children_end,
             offsetof(TestNode, prev),
             offsetof(TestNode, next),
-            (void**)&a.children_begin,
-            (void**)&a.children_end,
-            &a1);
-    CU_ASSERT_EQUAL(ret, 0);
+            &a1,
+            offsetof(TestNode, parent),
+            &a);
     CU_ASSERT_PTR_EQUAL(a.children_begin, &a1);
     CU_ASSERT_PTR_EQUAL(a1.parent, &a);
     CU_ASSERT_PTR_NOT_NULL(root.children_begin)