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/auth/rbac.service.spec.ts

@@ -0,0 +1,69 @@
+import { Test, TestingModule } from "@nestjs/testing";
+import { DatabaseService } from "../database/database.service";
+import { RbacService } from "./rbac.service";
+
+describe("RbacService", () => {
+	let service: RbacService;
+
+	const mockDb = {
+		select: jest.fn().mockReturnThis(),
+		from: jest.fn().mockReturnThis(),
+		innerJoin: jest.fn().mockReturnThis(),
+		where: jest.fn(),
+	};
+
+	beforeEach(async () => {
+		jest.clearAllMocks();
+		const module: TestingModule = await Test.createTestingModule({
+			providers: [
+				RbacService,
+				{
+					provide: DatabaseService,
+					useValue: {
+						db: mockDb,
+					},
+				},
+			],
+		}).compile();
+
+		service = module.get<RbacService>(RbacService);
+	});
+
+	it("should be defined", () => {
+		expect(service).toBeDefined();
+	});
+
+	describe("getUserRoles", () => {
+		it("should return user roles", async () => {
+			const userId = "user-id";
+			const mockRoles = [{ slug: "admin" }, { slug: "user" }];
+			mockDb.where.mockResolvedValue(mockRoles);
+
+			const result = await service.getUserRoles(userId);
+
+			expect(result).toEqual(["admin", "user"]);
+			expect(mockDb.select).toHaveBeenCalled();
+			expect(mockDb.from).toHaveBeenCalled();
+			expect(mockDb.innerJoin).toHaveBeenCalled();
+		});
+	});
+
+	describe("getUserPermissions", () => {
+		it("should return unique user permissions", async () => {
+			const userId = "user-id";
+			const mockPermissions = [
+				{ slug: "read" },
+				{ slug: "write" },
+				{ slug: "read" }, // Duplicate
+			];
+			mockDb.where.mockResolvedValue(mockPermissions);
+
+			const result = await service.getUserPermissions(userId);
+
+			expect(result).toEqual(["read", "write"]);
+			expect(mockDb.select).toHaveBeenCalled();
+			expect(mockDb.from).toHaveBeenCalled();
+			expect(mockDb.innerJoin).toHaveBeenCalledTimes(2);
+		});
+	});
+});