test: add comprehensive unit tests for core services

Added unit tests for the `api-keys`, `auth`, `categories`, `contents`, `favorites`, `media`, and `purge` services to improve test coverage and ensure core functionality integrity.

backend/src/categories/categories.service.spec.ts

@@ -0,0 +1,122 @@
+import { Test, TestingModule } from "@nestjs/testing";
+import { DatabaseService } from "../database/database.service";
+import { categories } from "../database/schemas";
+import { CategoriesService } from "./categories.service";
+import { CreateCategoryDto } from "./dto/create-category.dto";
+import { UpdateCategoryDto } from "./dto/update-category.dto";
+
+describe("CategoriesService", () => {
+	let service: CategoriesService;
+
+	const mockDb = {
+		select: jest.fn().mockReturnThis(),
+		from: jest.fn().mockReturnThis(),
+		where: jest.fn().mockReturnThis(),
+		limit: jest.fn().mockResolvedValue([]),
+		orderBy: jest.fn().mockResolvedValue([]),
+		insert: jest.fn().mockReturnThis(),
+		values: jest.fn().mockReturnThis(),
+		update: jest.fn().mockReturnThis(),
+		set: jest.fn().mockReturnThis(),
+		delete: jest.fn().mockReturnThis(),
+		returning: jest.fn().mockResolvedValue([]),
+	};
+
+	beforeEach(async () => {
+		jest.clearAllMocks();
+		const module: TestingModule = await Test.createTestingModule({
+			providers: [
+				CategoriesService,
+				{
+					provide: DatabaseService,
+					useValue: {
+						db: mockDb,
+					},
+				},
+			],
+		}).compile();
+
+		service = module.get<CategoriesService>(CategoriesService);
+	});
+
+	it("should be defined", () => {
+		expect(service).toBeDefined();
+	});
+
+	describe("findAll", () => {
+		it("should return all categories ordered by name", async () => {
+			const mockCategories = [{ name: "A" }, { name: "B" }];
+			mockDb.orderBy.mockResolvedValue(mockCategories);
+
+			const result = await service.findAll();
+
+			expect(result).toEqual(mockCategories);
+			expect(mockDb.select).toHaveBeenCalled();
+			expect(mockDb.from).toHaveBeenCalledWith(categories);
+		});
+	});
+
+	describe("findOne", () => {
+		it("should return a category by id", async () => {
+			const mockCategory = { id: "1", name: "Cat" };
+			mockDb.limit.mockResolvedValue([mockCategory]);
+
+			const result = await service.findOne("1");
+
+			expect(result).toEqual(mockCategory);
+		});
+
+		it("should return null if category not found", async () => {
+			mockDb.limit.mockResolvedValue([]);
+			const result = await service.findOne("999");
+			expect(result).toBeNull();
+		});
+	});
+
+	describe("create", () => {
+		it("should create a category and generate slug", async () => {
+			const dto: CreateCategoryDto = { name: "Test Category" };
+			mockDb.returning.mockResolvedValue([{ ...dto, slug: "test-category" }]);
+
+			const result = await service.create(dto);
+
+			expect(mockDb.insert).toHaveBeenCalledWith(categories);
+			expect(mockDb.values).toHaveBeenCalledWith({
+				name: "Test Category",
+				slug: "test-category",
+			});
+			expect(result[0].slug).toBe("test-category");
+		});
+	});
+
+	describe("update", () => {
+		it("should update a category and regenerate slug", async () => {
+			const id = "1";
+			const dto: UpdateCategoryDto = { name: "New Name" };
+			mockDb.returning.mockResolvedValue([{ id, ...dto, slug: "new-name" }]);
+
+			const result = await service.update(id, dto);
+
+			expect(mockDb.update).toHaveBeenCalledWith(categories);
+			expect(mockDb.set).toHaveBeenCalledWith(
+				expect.objectContaining({
+					name: "New Name",
+					slug: "new-name",
+				}),
+			);
+			expect(result[0].slug).toBe("new-name");
+		});
+	});
+
+	describe("remove", () => {
+		it("should remove a category", async () => {
+			const id = "1";
+			mockDb.returning.mockResolvedValue([{ id }]);
+
+			const result = await service.remove(id);
+
+			expect(mockDb.delete).toHaveBeenCalledWith(categories);
+			expect(result).toEqual([{ id }]);
+		});
+	});
+});