test: add unit tests for messaging, comments, events, and user services

- Added comprehensive unit tests for `MessagesService`, `CommentsService`, `EventsGateway`, and enhancements in `UsersService`.
- Ensured proper mocking and test coverage for newly introduced dependencies like `EventsGateway` and `RBACService`.

backend/src/messages/messages.service.spec.ts

@@ -0,0 +1,81 @@
+import { ForbiddenException } from "@nestjs/common";
+import { Test, TestingModule } from "@nestjs/testing";
+import { EventsGateway } from "../realtime/events.gateway";
+import { MessagesService } from "./messages.service";
+import { MessagesRepository } from "./repositories/messages.repository";
+
+describe("MessagesService", () => {
+	let service: MessagesService;
+	let repository: MessagesRepository;
+	let eventsGateway: EventsGateway;
+
+	const mockMessagesRepository = {
+		findConversationBetweenUsers: jest.fn(),
+		createConversation: jest.fn(),
+		addParticipant: jest.fn(),
+		createMessage: jest.fn(),
+		findAllConversations: jest.fn(),
+		isParticipant: jest.fn(),
+		findMessagesByConversationId: jest.fn(),
+	};
+
+	const mockEventsGateway = {
+		sendToUser: jest.fn(),
+	};
+
+	beforeEach(async () => {
+		const module: TestingModule = await Test.createTestingModule({
+			providers: [
+				MessagesService,
+				{ provide: MessagesRepository, useValue: mockMessagesRepository },
+				{ provide: EventsGateway, useValue: mockEventsGateway },
+			],
+		}).compile();
+
+		service = module.get<MessagesService>(MessagesService);
+		repository = module.get<MessagesRepository>(MessagesRepository);
+		eventsGateway = module.get<EventsGateway>(EventsGateway);
+	});
+
+	describe("sendMessage", () => {
+		it("should send message to existing conversation", async () => {
+			const senderId = "s1";
+			const dto = { recipientId: "r1", text: "hello" };
+			mockMessagesRepository.findConversationBetweenUsers.mockResolvedValue({ id: "conv1" });
+			mockMessagesRepository.createMessage.mockResolvedValue({ id: "m1", text: "hello" });
+
+			const result = await service.sendMessage(senderId, dto);
+
+			expect(result.id).toBe("m1");
+			expect(mockEventsGateway.sendToUser).toHaveBeenCalledWith("r1", "new_message", expect.anything());
+		});
+
+		it("should create new conversation if not exists", async () => {
+			const senderId = "s1";
+			const dto = { recipientId: "r1", text: "hello" };
+			mockMessagesRepository.findConversationBetweenUsers.mockResolvedValue(null);
+			mockMessagesRepository.createConversation.mockResolvedValue({ id: "new_conv" });
+			mockMessagesRepository.createMessage.mockResolvedValue({ id: "m1" });
+
+			await service.sendMessage(senderId, dto);
+
+			expect(mockMessagesRepository.createConversation).toHaveBeenCalled();
+			expect(mockMessagesRepository.addParticipant).toHaveBeenCalledTimes(2);
+		});
+	});
+
+	describe("getMessages", () => {
+		it("should return messages if user is participant", async () => {
+			mockMessagesRepository.isParticipant.mockResolvedValue(true);
+			mockMessagesRepository.findMessagesByConversationId.mockResolvedValue([{ id: "m1" }]);
+
+			const result = await service.getMessages("u1", "conv1");
+			expect(result).toHaveLength(1);
+		});
+
+		it("should throw ForbiddenException if user is not participant", async () => {
+			mockMessagesRepository.isParticipant.mockResolvedValue(false);
+			await expect(service.getMessages("u1", "conv1")).rejects.toThrow(ForbiddenException);
+		});
+	});
+});