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/sessions/sessions.service.spec.ts

@@ -0,0 +1,124 @@
+jest.mock("@noble/post-quantum/ml-kem.js", () => ({
+	ml_kem768: {
+		keygen: jest.fn(),
+		encapsulate: jest.fn(),
+		decapsulate: jest.fn(),
+	},
+}));
+
+jest.mock("jose", () => ({
+	SignJWT: jest.fn(),
+	jwtVerify: jest.fn(),
+}));
+
+import { UnauthorizedException } from "@nestjs/common";
+import { Test, TestingModule } from "@nestjs/testing";
+import { CryptoService } from "../crypto/crypto.service";
+import { DatabaseService } from "../database/database.service";
+import { SessionsService } from "./sessions.service";
+
+describe("SessionsService", () => {
+	let service: SessionsService;
+
+	const mockDb = {
+		insert: jest.fn(),
+		select: jest.fn(),
+		update: jest.fn(),
+	};
+
+	const mockCryptoService = {
+		generateJwt: jest.fn().mockResolvedValue("mock-jwt"),
+		hashIp: jest.fn().mockResolvedValue("mock-ip-hash"),
+	};
+
+	beforeEach(async () => {
+		jest.clearAllMocks();
+
+		const chain = {
+			insert: jest.fn().mockReturnThis(),
+			values: jest.fn().mockReturnThis(),
+			returning: jest.fn().mockReturnThis(),
+			select: jest.fn().mockReturnThis(),
+			from: jest.fn().mockReturnThis(),
+			where: jest.fn().mockReturnThis(),
+			limit: jest.fn().mockReturnThis(),
+			update: jest.fn().mockReturnThis(),
+			set: jest.fn().mockReturnThis(),
+			// biome-ignore lint/suspicious/noThenProperty: Fine for testing purposes
+			then: jest.fn().mockImplementation(function (cb) {
+				return Promise.resolve(this).then(cb);
+			}),
+		};
+
+		const mockImplementation = () => Object.assign(Promise.resolve([]), chain);
+		for (const mock of Object.values(chain)) {
+			if (mock !== chain.then) {
+				mock.mockImplementation(mockImplementation);
+			}
+		}
+		Object.assign(mockDb, chain);
+
+		const module: TestingModule = await Test.createTestingModule({
+			providers: [
+				SessionsService,
+				{ provide: DatabaseService, useValue: { db: mockDb } },
+				{ provide: CryptoService, useValue: mockCryptoService },
+			],
+		}).compile();
+
+		service = module.get<SessionsService>(SessionsService);
+	});
+
+	it("should be defined", () => {
+		expect(service).toBeDefined();
+	});
+
+	describe("createSession", () => {
+		it("should create a session", async () => {
+			mockDb.returning.mockResolvedValue([{ id: "s1", refreshToken: "mock-jwt" }]);
+			const result = await service.createSession("u1", "agent", "1.2.3.4");
+			expect(result.id).toBe("s1");
+			expect(mockCryptoService.generateJwt).toHaveBeenCalledWith(
+				{ sub: "u1", type: "refresh" },
+				"7d",
+			);
+		});
+	});
+
+	describe("refreshSession", () => {
+		it("should refresh a valid session", async () => {
+			const expiresAt = new Date();
+			expiresAt.setDate(expiresAt.getDate() + 1);
+			const session = { id: "s1", userId: "u1", expiresAt, isValid: true };
+
+			mockDb.where.mockImplementation(() => {
+				const chain = {
+					limit: jest.fn().mockReturnThis(),
+					returning: jest
+						.fn()
+						.mockResolvedValue([{ ...session, refreshToken: "new-jwt" }]),
+					// biome-ignore lint/suspicious/noThenProperty: Fine for testing purposes
+					then: jest.fn().mockResolvedValue(session),
+				};
+				return Object.assign(Promise.resolve([session]), chain);
+			});
+
+			const result = await service.refreshSession("old-jwt");
+			expect(result.refreshToken).toBe("new-jwt");
+		});
+
+		it("should throw UnauthorizedException if session not found", async () => {
+			mockDb.where.mockImplementation(() => {
+				const chain = {
+					limit: jest.fn().mockReturnThis(),
+					// biome-ignore lint/suspicious/noThenProperty: Fine for testing purposes
+					then: jest.fn().mockResolvedValue(null),
+				};
+				return Object.assign(Promise.resolve([]), chain);
+			});
+			await expect(service.refreshSession("invalid")).rejects.toThrow(
+				UnauthorizedException,
+			);
+		});
+	});
+});