memegoat/backend/src/favorites/favorites.service.spec.ts

import { ConflictException, NotFoundException } from "@nestjs/common";
import { Test, TestingModule } from "@nestjs/testing";
import { DatabaseService } from "../database/database.service";
import { FavoritesService } from "./favorites.service";

describe("FavoritesService", () => {
	let service: FavoritesService;

	const mockDb = {
		select: jest.fn(),
		from: jest.fn(),
		where: jest.fn(),
		limit: jest.fn(),
		offset: jest.fn(),
		innerJoin: jest.fn(),
		insert: jest.fn(),
		values: jest.fn(),
		delete: jest.fn(),
		returning: jest.fn(),
	};

	beforeEach(async () => {
		jest.clearAllMocks();

		const chain = {
			select: jest.fn().mockReturnThis(),
			from: jest.fn().mockReturnThis(),
			where: jest.fn().mockReturnThis(),
			limit: jest.fn().mockReturnThis(),
			offset: jest.fn().mockReturnThis(),
			innerJoin: jest.fn().mockReturnThis(),
			insert: jest.fn().mockReturnThis(),
			values: jest.fn().mockReturnThis(),
			delete: jest.fn().mockReturnThis(),
			returning: jest.fn().mockReturnThis(),
		};

		const mockImplementation = () => Object.assign(Promise.resolve([]), chain);
		for (const mock of Object.values(chain)) {
			mock.mockImplementation(mockImplementation);
		}
		Object.assign(mockDb, chain);

		const module: TestingModule = await Test.createTestingModule({
			providers: [
				FavoritesService,
				{ provide: DatabaseService, useValue: { db: mockDb } },
			],
		}).compile();

		service = module.get<FavoritesService>(FavoritesService);
	});

	it("should be defined", () => {
		expect(service).toBeDefined();
	});

	describe("addFavorite", () => {
		it("should add a favorite", async () => {
			mockDb.limit.mockResolvedValue([{ id: "content1" }]);
			mockDb.returning.mockResolvedValue([
				{ userId: "u1", contentId: "content1" },
			]);

			const result = await service.addFavorite("u1", "content1");

			expect(result).toEqual([{ userId: "u1", contentId: "content1" }]);
		});

		it("should throw NotFoundException if content does not exist", async () => {
			mockDb.limit.mockResolvedValue([]);
			await expect(service.addFavorite("u1", "invalid")).rejects.toThrow(
				NotFoundException,
			);
		});

		it("should throw ConflictException on duplicate favorite", async () => {
			mockDb.limit.mockResolvedValue([{ id: "content1" }]);
			mockDb.returning.mockRejectedValue(new Error("Duplicate"));
			await expect(service.addFavorite("u1", "content1")).rejects.toThrow(
				ConflictException,
			);
		});
	});

	describe("removeFavorite", () => {
		it("should remove a favorite", async () => {
			mockDb.returning.mockResolvedValue([{ userId: "u1", contentId: "c1" }]);
			const result = await service.removeFavorite("u1", "c1");
			expect(result).toEqual({ userId: "u1", contentId: "c1" });
		});

		it("should throw NotFoundException if favorite not found", async () => {
			mockDb.returning.mockResolvedValue([]);
			await expect(service.removeFavorite("u1", "c1")).rejects.toThrow(
				NotFoundException,
			);
		});
	});
});