hc-chat-api/src/app.controller.spec.ts

import { Test, TestingModule } from '@nestjs/testing'
import { AppController } from './app.controller'
import { AppService } from './app.service'

class MockResponse {
    res: any
    constructor() {
        this.res = {}
    }
    status = jest
        .fn()
        .mockReturnThis()
        .mockImplementationOnce((code) => {
            this.res.code = code
            return this
        })
    send = jest
        .fn()
        .mockReturnThis()
        .mockImplementationOnce((message) => {
            this.res.message = message
            return this
        })
    json = jest
        .fn()
        .mockReturnThis()
        .mockImplementationOnce((json) => {
            this.res.json = json
            return this
        })
}

describe('AppController', () => {
    let appController: AppController
    let appService: AppService
    const response = new MockResponse()

    beforeEach(async () => {
        const app: TestingModule = await Test.createTestingModule({
            controllers: [AppController],
            providers: [
                {
                    provide: AppService,
                    useValue: {
                        getHello: jest.fn(() => {}),
                        getSecureResource: jest.fn(() => {})
                    }
                }
            ]
        }).compile()

        appController = app.get<AppController>(AppController)
        appService = app.get<AppService>(AppService)
    })

    describe('root', () => {
        it('should be defined', () => {
            expect(appController).toBeDefined()
        })

        it('should call method getHello() in AppService', () => {
            const createSpy = jest.spyOn(appService, 'getHello')

            appController.getHello(response as any)
            expect(createSpy).toHaveBeenCalled()
        })

        it('should call method getProtectedResource() in AppService', () => {
            const createSpy = jest.spyOn(appService, 'getSecureResource')

            appController.getProtectedResource(response as any)
            expect(createSpy).toHaveBeenCalled()
        })
    })
})