diff --git a/lib/util/Graph.test.ts b/lib/util/Graph.test.ts
new file mode 100644
index 0000000..e52880c
--- /dev/null
+++ b/lib/util/Graph.test.ts
@@ -0,0 +1,47 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { Graph } from './Graph.js';
+
+describe('Graph', () => {
+  it('should add edges correctly', () => {
+    const graph = new Graph();
+    graph.addEdge('A', 'B');
+    graph.addEdge('A', 'C');
+
+    assert.equal(graph.vertexes.size, 3);
+    assert.deepEqual(graph.vertexes.get('A')?.to, new Set(['B', 'C']));
+    assert.deepEqual(graph.vertexes.get('B')?.from, new Set(['A']));
+    assert.deepEqual(graph.vertexes.get('C')?.from, new Set(['A']));
+  });
+
+  it('should delete vertex correctly', () => {
+    const graph = new Graph();
+    graph.addEdge('A', 'B');
+    graph.addEdge('A', 'C');
+    graph.addEdge('B', 'C');
+
+    graph.deleteVertex('A');
+
+    assert.equal(graph.vertexes.size, 2);
+    assert.equal(graph.vertexes.has('A'), false);
+    assert.deepEqual(graph.vertexes.get('B')?.to, new Set(['C']));
+    assert.deepEqual(graph.vertexes.get('C')?.from, new Set(['B']));
+  });
+
+  it('should remove vertexes without any edges', () => {
+    const graph = new Graph();
+    graph.addEdge('A', 'B');
+    graph.addEdge('A', 'C');
+    graph.addEdge('B', 'C');
+    graph.deleteVertex('B');
+
+    assert.equal(graph.vertexes.size, 2);
+    assert.equal(graph.vertexes.has('B'), false);
+    assert.equal(graph.vertexes.has('A'), true);
+    assert.equal(graph.vertexes.has('C'), true);
+    assert.deepEqual(graph.vertexes.get('A')?.to, new Set(['C']));
+    assert.deepEqual(graph.vertexes.get('A')?.from.size, 0);
+    assert.equal(graph.vertexes.get('C')?.to.size, 0);
+    assert.deepEqual(graph.vertexes.get('C')?.from, new Set(['A']));
+  });
+});