write and add unit-tests

.gitignore

@@ -1,3 +1,4 @@
 node_modules
 *.log
 .DS_Store
+/coverage

TypeScript/1-Repository.ts

@@ -1,8 +1,8 @@
 // Entity DAO
 
-type RawUser = { id: number; name: string };
+export type RawUser = { id: number; name: string };
 
-class UserDAO {
+export class UserDAO {
   constructor(public options: { fake: true }) {}
 
   getById(id: number): Promise<RawUser> {
@@ -13,13 +13,13 @@ class UserDAO {
 
 // Domain Entity
 
-class User {
+export class User {
   constructor(public id: number, public name: string) {}
 }
 
 // Repository
 
-class UserRepository {
+export class UserRepository {
   constructor(private dao: UserDAO) {}
 
   async findById(id: number): Promise<User> {

TypeScript/__tests__/1-Repository.test.ts

@@ -0,0 +1,41 @@
+import { UserDAO, UserRepository, User } from '../1-Repository';
+
+describe('UserDAO', () => {
+  it('should return RawUser when fake=true', async () => {
+    const dao = new UserDAO({ fake: true });
+    const raw = await dao.getById(42);
+    expect(raw).toEqual({ id: 42, name: 'Marcus Aurelius' });
+  });
+
+  it('should throw an error when fake=false', () => {
+    const dao = new UserDAO({ fake: false as any });
+    expect(() => dao.getById(1)).toThrow('Not a fake');
+  });
+});
+
+describe('UserRepository', () => {
+  it('should return a User instance for valid data', async () => {
+    const dao = new UserDAO({ fake: true });
+    const repo = new UserRepository(dao);
+    const user = await repo.findById(7);
+    expect(user).toBeInstanceOf(User);
+    expect(user).toMatchObject({ id: 7, name: 'Marcus Aurelius' });
+  });
+
+  it('should propagate errors from DAO when it throws', async () => {
+    const throwingDao = {
+      getById: jest.fn().mockRejectedValue(new Error('Not a fake'))
+    } as unknown as UserDAO;
+    const repo = new UserRepository(throwingDao);
+    await expect(repo.findById(3)).rejects.toThrow('Not a fake');
+  });
+
+  it('should throw "Record not found" if DAO returns null/undefined', async () => {
+    const nullDao = {
+      getById: jest.fn().mockResolvedValue(null)
+    } as unknown as UserDAO;
+    const repo = new UserRepository(nullDao);
+    await expect(repo.findById(5))
+      .rejects.toThrow('Record not found: User(5)');
+  });
+});

jest.config.js

@@ -0,0 +1,7 @@
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  roots: ['<rootDir>/TypeScript'],
+  testMatch: ['**/?(*.)+(spec|test).[t]s'],
+  moduleFileExtensions: ['ts', 'js', 'json', 'node'],
+};