Merge pull request #9 from Eric-Zhang-Developer/feature/backend-logic

Feature/backend logic

Author: Eric-Zhang-Developer

jest.config.mjs

@@ -0,0 +1,12 @@
+import nextJest from "next/jest.js";
+
+const createJestConfig = nextJest({
+  dir: "./",
+});
+
+const config = {
+  testEnvironment: "jest-environment-jsdom",
+  setupFilesAfterEnv: ["<rootDir>/jest.setup.js"],
+};
+
+export default createJestConfig(config);

jest.setup.js

@@ -0,0 +1 @@
+import "@testing-library/jest-dom";

package-lock.json

@@ -6,7 +6,8 @@
     "dev": "next dev --turbopack",
     "build": "next build",
     "start": "next start",
-    "lint": "next lint"
+    "lint": "next lint",
+    "test": "jest"
   },
   "dependencies": {
     "next": "15.2.3",
@@ -17,11 +18,16 @@
   "devDependencies": {
     "@eslint/eslintrc": "^3",
     "@tailwindcss/postcss": "^4",
+    "@testing-library/jest-dom": "^6.6.3",
+    "@testing-library/react": "^16.3.0",
+    "@types/jest": "^30.0.0",
     "@types/node": "^20",
     "@types/react": "^19",
     "@types/react-dom": "^19",
     "eslint": "^9",
     "eslint-config-next": "15.2.3",
+    "jest": "^30.0.2",
+    "jest-environment-jsdom": "^30.0.2",
     "tailwindcss": "^4",
     "typescript": "^5"
   }

package.json

@@ -0,0 +1,64 @@
+import Compare from "../comparison";
+
+describe("Comparison Tests", () => {
+  describe("Core Logic", () => {
+    it("should return an array of users who are in the following list but not the followers list", () => {
+      const followers = ["Alice", "Brenda"];
+      const following = ["Alice", "Brenda", "Charlie"];
+      const result = Compare(following, followers);
+
+      expect(result).toEqual(["Charlie"]);
+    });
+
+    it("should return an empty array when both lists are empty", () => {
+      const followers: string[] = [];
+      const following: string[] = [];
+      const result = Compare(following, followers);
+
+      expect(result).toEqual([]);
+    });
+
+    it("should return the entire following list if there are not followers to compare to", () => {
+      const followers: string[] = [];
+      const following = ["Alice", "Brenda", "Charlie", "David"];
+      const result = Compare(following, followers);
+
+      expect(result).toEqual(following);
+    });
+  });
+
+  describe("Business Logic", () => {
+    it("should return ex-friend if my ex-friend unfollowed me", () => {
+      const followers = ["friend"];
+      const following = ["friend", "ex_friend"];
+      const result = Compare(following, followers);
+
+      expect(result).toEqual(["ex_friend"]);
+    });
+
+    it("should return only celebrities that I expect when no one unfollows me", () => {
+      const followers = ["friend", "friend_2"];
+      const following = ["friend", "friend_2", "POTUS", "Tom_Cruise"];
+      const result = Compare(following, followers);
+
+      expect(result).toEqual(["POTUS", "Tom_Cruise"]);
+    });
+
+    it("should return no accounts when I don't follow accounts who follow me", () => {
+      const followers = ["friend", "friend_2", "spam_bot"];
+      const following = ["friend", "friend_2"];
+      const result = Compare(following, followers);
+
+      expect(result).toEqual([]);
+    });
+
+    it("should return ex-friend AND celebrity accounts when my ex-friend unfollows me and I follow brand / celerity accounts I don't expect to follow me back", () => {
+      const followers = ["friend"];
+      const following = ["friend", "ex_friend", "POTUS", "Tom_Cruise"];
+      const result = Compare(following, followers);
+
+      expect(result).toEqual(["ex_friend", "POTUS", "Tom_Cruise"]);
+    });
+
+  });
+});

src/lib/__tests__/comparison.test.ts

@@ -0,0 +1,39 @@
+import ExtractNamesFromJson from "../extractNamesFromJson";
+
+const data = [
+  {
+    title: "",
+    media_list_data: [],
+    string_list_data: [
+      {
+        href: "https://www.instagram.com/POTUS",
+        value: "POTUS",
+        timestamp: 2248397812,
+      },
+    ],
+  },
+  {
+    title: "",
+    media_list_data: [],
+    string_list_data: [
+      {
+        href: "https://www.instagram.com/NASA",
+        value: "NASA",
+        timestamp: 1267694584,
+      },
+    ],
+  },
+];
+
+// Other tests are not necessary here because Typescript already validates the json as formed properly
+// If the json is bad then we throw an error outside 
+
+describe("Extract Names Function Tests", () => {
+  describe("Core Logic", () => {
+    // Happy path
+    it("should return an array of usernames when a proper json is input", () => {
+      const result = ExtractNamesFromJson(data);
+      expect(result).toEqual(["POTUS", "NASA"]);
+    });
+  });
+});

src/lib/__tests__/extractNamesFromJson.test.ts

@@ -0,0 +1,12 @@
+// Calculates the difference between two lists of users to find who is not following back.
+// Uses a set to reduce time from O(n*m) to O(n + m)
+// For each user name in your following it checks to see if its in the followers set, O(n) time total
+export default function Compare(followingData: string[], followerData: string[]) {
+  const followerDataSet = new Set(followerData);
+  const doesNotFollowBack = followingData.filter(userName => {
+    return !followerDataSet.has(userName);
+  });
+  return doesNotFollowBack;
+}
+
+

src/lib/comparison.ts

@@ -0,0 +1,19 @@
+// The reason for these interfaces is so that typescript neatly throws an error when a user 
+// adds a json that is not a followers.json or following.json format 
+
+interface ExpectedJSON {
+  title: string;
+  media_list_data: unknown[];
+  string_list_data: stringListData[];
+}
+
+interface stringListData{
+  href: string;
+  value: string;
+  timestamp: number;
+}
+
+export default function ExtractNamesFromJson(json: ExpectedJSON[]) {
+  const usernames = json.map(user => user.string_list_data[0].value);
+  return usernames;
+}