fix: apply delay to cached responses

src/domain/usecase/RespondToRequest.test.ts

@@ -1,13 +1,17 @@
 import { ResponseRepository } from '../repository';
 import { NetworkService } from '../service';
 
-import { RespondToRequest } from './RespondToRequest';
 import { Response, Request } from '../entity';
+import { RespondToRequest } from './RespondToRequest';
+import { wait } from '../../util/timers';
+
+jest.mock('../../util/timers');
 
 let responseRepository: ResponseRepository;
 let networkService: NetworkService;
 
 beforeEach(() => {
+  (wait as jest.Mock).mockReset();
   responseRepository = {
     getResponseForRequest: jest.fn().mockResolvedValue(null),
     persistResponseForRequest: jest.fn().mockResolvedValue(null),
@@ -26,9 +30,11 @@ describe('when the response is in the cache', () => {
 
   it('should return the response from the cache, without using the network', async () => {
     // Given
+    const delay = 1000;
     const useCase = new RespondToRequest({
       responseRepository,
       networkService,
+      delay,
     });
     const method = 'GET';
     const url = '/beers/1';
@@ -47,6 +53,8 @@ describe('when the response is in the cache', () => {
     expect(responseRepository.getResponseForRequest).toHaveBeenCalledWith(
       new Request(method, url, headers, body)
     );
+    expect(wait).toHaveBeenCalledTimes(1);
+    expect(wait).toHaveBeenCalledWith(1000);
 
     expect(networkService.executeRequest).not.toHaveBeenCalled();
   });
@@ -63,9 +71,11 @@ describe('when no response is in the cache', () => {
   });
 
   it('should fetch the reponse from the network and store it in the cache', async () => {
+    const delay = 1000;
     const useCase = new RespondToRequest({
       responseRepository,
       networkService,
+      delay,
     });
     const method = 'GET';
     const url = '/beers/1';
@@ -92,5 +102,8 @@ describe('when no response is in the cache', () => {
       new Request(method, url, headers, body),
       new Response(200, { 'cache-control': 'something' }, 'some body')
     );
+
+    expect(wait).toHaveBeenCalledTimes(1);
+    expect(wait).toHaveBeenCalledWith(1000);
   });
 });

src/domain/usecase/RespondToRequest.ts

@@ -1,4 +1,5 @@
 import { logger } from '../../util/logger';
+import { wait } from '../../util/timers';
 
 import { Method, Response, Request } from '../entity';
 import { ResponseRepository } from '../repository';
@@ -7,6 +8,7 @@ import { NetworkService } from '../service';
 interface Dependencies {
   responseRepository: ResponseRepository;
   networkService: NetworkService;
+  delay: number;
 }
 
 export interface Headers {
@@ -16,10 +18,16 @@ export interface Headers {
 export class RespondToRequest {
   private responseRepository: ResponseRepository;
   private networkService: NetworkService;
+  private delay: number;
 
-  public constructor({ responseRepository, networkService }: Dependencies) {
+  public constructor({
+    responseRepository,
+    networkService,
+    delay,
+  }: Dependencies) {
     this.responseRepository = responseRepository;
     this.networkService = networkService;
+    this.delay = delay;
   }
 
   public async execute(
@@ -33,16 +41,22 @@ export class RespondToRequest {
     const cachedResponse = await this.responseRepository.getResponseForRequest(
       request
     );
+    let response: Response;
 
     if (cachedResponse) {
+      response = cachedResponse;
       logger.debug('Using response from the cache');
-      return cachedResponse;
+    } else {
+      logger.debug('Fetching response from the network');
+      response = await this.networkService.executeRequest(request);
+
+      await this.responseRepository.persistResponseForRequest(
+        request,
+        response
+      );
     }
 
-    logger.debug('Fetching response from the network');
-    const response = await this.networkService.executeRequest(request);
-
-    await this.responseRepository.persistResponseForRequest(request, response);
+    await wait(this.delay);
 
     return response;
   }

src/infrastructure/service/NetworkServiceAxios.ts

@@ -6,16 +6,13 @@ import { Request, Response } from '../../domain/entity';
 
 interface Dependencies {
   targetUrl: string;
-  delay: number;
 }
 
 export class NetworkServiceAxios implements NetworkService {
   private targetUrl: string;
-  private delay: number;
 
-  public constructor({ targetUrl, delay }: Dependencies) {
+  public constructor({ targetUrl }: Dependencies) {
     this.targetUrl = targetUrl;
-    this.delay = delay;
   }
 
   public async executeRequest(request: Request): Promise<Response> {
@@ -27,8 +24,6 @@ export class NetworkServiceAxios implements NetworkService {
     // For now we do not support gzip
     delete headers['accept-encoding'];
 
-    await new Promise(resolve => setTimeout(resolve, this.delay));
-
     const axiosResponse = await axios({
       data: request.body,
       url: `${this.targetUrl}${request.url}`,

src/util/__mocks__/timers.ts

@@ -0,0 +1 @@
+export const wait = jest.fn();

src/util/timers.ts

@@ -0,0 +1,2 @@
+export const wait = (time: number) =>
+  new Promise(resolve => setTimeout(resolve, time));