feat: ✨ add users service

apps/users-application/src/users/users.service.spec.ts

@@ -0,0 +1,29 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { UsersService } from './users.service';
+import { User } from './models/user.model';
+
+describe('UsersService', () => {
+  let service: UsersService;
+
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      providers: [UsersService],
+    }).compile();
+
+    service = module.get<UsersService>(UsersService);
+  });
+
+  it('should be defined', () => {
+    expect(service).toBeDefined();
+  });
+
+  it('should return a user by id', () => {
+    const user: User = service.findById(1);
+    expect(user).toEqual({ id: 1, name: 'John Doe' });
+  });
+
+  it('should return undefined if user is not found', () => {
+    const user: User = service.findById(3);
+    expect(user).toBeUndefined();
+  });
+});

apps/users-application/src/users/users.service.ts

@@ -0,0 +1,14 @@
+import { Injectable } from '@nestjs/common';
+import { User } from './models/user.model';
+
+@Injectable()
+export class UsersService {
+  private users: User[] = [
+    { id: 1, name: 'John Doe' },
+    { id: 2, name: 'Richard Roe' },
+  ];
+
+  findById(id: number): User | undefined {
+    return this.users.find((user) => user.id === Number(id));
+  }
+}