add: unit and integration testing

app/test/filter-json.test.js

@@ -0,0 +1,37 @@
+const { filterJson } = require("../src/search");
+
+describe("filterJson", () => {
+  // deliberately adding an extra property that is not supposed to be there
+  test("keeps only url, title, and content", () => {
+    const input = [
+      {
+        url: "https://example.com",
+        title: "Example",
+        content: "Some content",
+        engine: "startpage",
+        score: 0.9
+      }
+    ];
+
+    expect(filterJson(input)).toEqual([
+      {
+        url: "https://example.com",
+        title: "Example",
+        content: "Some content"
+      }
+    ]);
+  });
+
+  test("returns an empty array for empty input", () => {
+    expect(filterJson([])).toEqual([]);
+  });
+
+  test("handles multiple results", () => {
+    const input = [
+      { url: "one", title: "One", content: "First" },
+      { url: "two", title: "Two", content: "Second" }
+    ];
+
+    expect(filterJson(input)).toEqual(input);
+  });
+});