test: add unit tests for CoursesService

src/courses/courses.service.spec.ts

@@ -0,0 +1,177 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { getRepositoryToken } from '@nestjs/typeorm';
+import { NotFoundException } from '@nestjs/common';
+import { EventEmitter2 } from '@nestjs/event-emitter';
+import { CoursesService } from './courses.service';
+import { Course } from './entities/course.entity';
+import { CachingService } from '../caching/caching.service';
+import { CacheInvalidationService } from '../caching/invalidation/invalidation.service';
+
+const mockRepo = () => ({
+  create: jest.fn(),
+  save: jest.fn(),
+  findOne: jest.fn(),
+  find: jest.fn(),
+  findByIds: jest.fn(),
+  count: jest.fn(),
+  softDelete: jest.fn(),
+  createQueryBuilder: jest.fn(),
+  manager: {
+    transaction: jest.fn(),
+    getRepository: jest.fn(),
+  },
+});
+
+const mockCaching = () => ({
+  getOrSet: jest.fn().mockImplementation((_key: string, fn: () => any) => fn()),
+  invalidate: jest.fn().mockResolvedValue(undefined),
+});
+
+const mockInvalidation = () => ({
+  invalidateByPattern: jest.fn().mockResolvedValue(undefined),
+  invalidate: jest.fn().mockResolvedValue(undefined),
+});
+
+describe('CoursesService', () => {
+  let service: CoursesService;
+  let repo: ReturnType<typeof mockRepo>;
+  let caching: ReturnType<typeof mockCaching>;
+  let emitter: { emit: jest.Mock };
+
+  beforeEach(async () => {
+    repo = mockRepo();
+    caching = mockCaching();
+    emitter = { emit: jest.fn() };
+
+    const module: TestingModule = await Test.createTestingModule({
+      providers: [
+        CoursesService,
+        { provide: getRepositoryToken(Course), useValue: repo },
+        { provide: CachingService, useValue: caching },
+        { provide: CacheInvalidationService, useValue: mockInvalidation() },
+        { provide: EventEmitter2, useValue: emitter },
+      ],
+    }).compile();
+
+    service = module.get<CoursesService>(CoursesService);
+  });
+
+  afterEach(() => jest.clearAllMocks());
+
+  // ─── create ──────────────────────────────────────────────────────────────
+
+  describe('create', () => {
+    it('creates and returns a course', async () => {
+      const dto = { title: 'NestJS Basics', instructorId: 'inst-1' };
+      const entity = { id: 'c1', title: 'NestJS Basics', instructor: { id: 'inst-1' } };
+      repo.create.mockReturnValue(entity);
+      repo.save.mockResolvedValue(entity);
+
+      const result = await service.create(dto);
+      expect(repo.create).toHaveBeenCalledWith({
+        ...dto,
+        instructor: { id: 'inst-1' },
+      });
+      expect(repo.save).toHaveBeenCalledWith(entity);
+      expect(emitter.emit).toHaveBeenCalled();
+      expect(result).toEqual(entity);
+    });
+  });
+
+  // ─── findOne ─────────────────────────────────────────────────────────────
+
+  describe('findOne', () => {
+    it('returns a course when found', async () => {
+      const entity = { id: 'c1', title: 'Course 1', modules: [] };
+      repo.findOne.mockResolvedValue(entity);
+
+      const result = await service.findOne('c1');
+      expect(result).toEqual(entity);
+      expect(repo.findOne).toHaveBeenCalledWith({
+        where: { id: 'c1' },
+        relations: ['instructor', 'modules', 'modules.lessons'],
+      });
+    });
+
+    it('throws NotFoundException when course does not exist', async () => {
+      repo.findOne.mockResolvedValue(null);
+      await expect(service.findOne('missing')).rejects.toThrow(NotFoundException);
+    });
+  });
+
+  // ─── findByIds ───────────────────────────────────────────────────────────
+
+  describe('findByIds', () => {
+    it('returns empty array for empty input', async () => {
+      const result = await service.findByIds([]);
+      expect(result).toEqual([]);
+      expect(repo.findByIds).not.toHaveBeenCalled();
+    });
+
+    it('delegates to repository for non-empty ids', async () => {
+      const courses = [{ id: 'c1' }, { id: 'c2' }];
+      repo.findByIds.mockResolvedValue(courses);
+      const result = await service.findByIds(['c1', 'c2']);
+      expect(result).toEqual(courses);
+    });
+  });
+
+  // ─── update ──────────────────────────────────────────────────────────────
+
+  describe('update', () => {
+    it('throws NotFoundException when course does not exist', async () => {
+      repo.findOne.mockResolvedValue(null);
+      await expect(service.update('missing', { title: 'New' })).rejects.toThrow(NotFoundException);
+    });
+
+    it('updates and returns the course', async () => {
+      const entity = { id: 'c1', title: 'Old', modules: [] };
+      repo.findOne.mockResolvedValue(entity);
+      repo.save.mockResolvedValue({ ...entity, title: 'New' });
+
+      const result = await service.update('c1', { title: 'New' });
+      expect(result.title).toBe('New');
+      expect(emitter.emit).toHaveBeenCalled();
+    });
+  });
+
+  // ─── remove ──────────────────────────────────────────────────────────────
+
+  describe('remove', () => {
+    it('throws NotFoundException when course does not exist', async () => {
+      repo.findOne.mockResolvedValue(null);
+      await expect(service.remove('missing')).rejects.toThrow(NotFoundException);
+    });
+
+    it('runs a transaction and emits event', async () => {
+      const entity = { id: 'c1', modules: [] };
+      repo.findOne.mockResolvedValue(entity);
+      repo.manager.transaction.mockImplementation(async (fn: any) => fn(repo.manager));
+      repo.manager.getRepository.mockReturnValue({ softDelete: jest.fn().mockResolvedValue(undefined) });
+
+      await service.remove('c1');
+      expect(repo.manager.transaction).toHaveBeenCalledTimes(1);
+      expect(emitter.emit).toHaveBeenCalled();
+    });
+  });
+
+  // ─── getAnalytics ────────────────────────────────────────────────────────
+
+  describe('getAnalytics', () => {
+    it('returns aggregated analytics', async () => {
+      repo.count
+        .mockResolvedValueOnce(10)
+        .mockResolvedValueOnce(6);
+
+      const qb: any = {
+        leftJoin: jest.fn().mockReturnThis(),
+        select: jest.fn().mockReturnThis(),
+        getRawOne: jest.fn().mockResolvedValue({ totalEnrollments: '42' }),
+      };
+      repo.createQueryBuilder.mockReturnValue(qb);
+
+      const result = await service.getAnalytics();
+      expect(result).toEqual({ totalCourses: 10, publishedCourses: 6, totalEnrollments: 42 });
+    });
+  });
+});