diff --git a/nestjs-BE/server/src/crdt/tree.spec.ts b/nestjs-BE/server/src/crdt/tree.spec.ts
new file mode 100644
index 00000000..cf9da0ce
--- /dev/null
+++ b/nestjs-BE/server/src/crdt/tree.spec.ts
@@ -0,0 +1,19 @@
+import { Tree } from './tree';
+
+it('isAncestor', () => {
+  const tree = new Tree<string>();
+
+  tree.addNode('a', 'root', 'test');
+  tree.addNode('b', 'a', 'test');
+  tree.addNode('c', 'b', 'test');
+  tree.addNode('d', 'a', 'test');
+  tree.addNode('e', 'b', 'test');
+
+  expect(tree.isAncestor('c', 'a')).toBeTruthy();
+  expect(tree.isAncestor('c', 'root')).toBeTruthy();
+  expect(tree.isAncestor('d', 'root')).toBeTruthy();
+  expect(tree.isAncestor('d', 'a')).toBeTruthy();
+  expect(tree.isAncestor('c', 'e')).toBeFalsy();
+  expect(tree.isAncestor('e', 'c')).toBeFalsy();
+  expect(tree.isAncestor('c', 'd')).toBeFalsy();
+});