add: unit and integration testing

app/test/app.test.js

@@ -0,0 +1,48 @@
+const request = require("supertest");
+const app = require("../src/app");
+
+describe("GET /search", () => {
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  test("returns 400 when query is missing", async () => {
+    const response = await request(app).get("/search");
+
+    expect(response.status).toBe(400);
+    expect(response.text).toBe("Missing search query");
+  });
+
+  test("returns filtered search results", async () => {
+    global.fetch = jest.fn().mockResolvedValue({
+      json: jest.fn().mockResolvedValue({
+        results: [
+          {
+            url: "https://example.com",
+            title: "Example",
+            content: "Content",
+            irrelevant: "removed"
+          }
+        ]
+      })
+    });
+
+    const response = await request(app)
+      .get("/search")
+      .query({ query: "nodejs" });
+
+    expect(response.status).toBe(200);
+    expect(response.headers["content-type"]).toMatch(/application\/json/);
+    expect(response.headers["content-disposition"]).toContain(
+      'attachment; filename="output.json"'
+    );
+
+    expect(response.body).toEqual([
+      {
+        url: "https://example.com",
+        title: "Example",
+        content: "Content"
+      }
+    ]);
+  });
+});