How do I test a JSONP HTTP request in Angular?
I'm using the HttpClientModule and HttpClientJsonpModule to make a JSONP HTTP request in a service.
app.module.ts
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { HttpClientModule, HttpClientJsonpModule } from '@angular/common/http';
import { AppComponent } from './app.component';
@NgModule({
declarations: [
AppComponent
],
imports: [
BrowserModule,
HttpClientModule,
HttpClientJsonpModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }
This service uses the jsonp method from the HttpClient class to get a JSONP response from the specified URL. I think that this response is intercepted by JsonpInterceptor and sent to the JsonpClientBackend where the request is handled.
example.service.ts
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
@Injectable()
export class ExampleService {
url = "https://archive.org/index.php?output=json&callback=callback";
constructor(private http: HttpClient) { }
getData() {
return this.http.jsonp(this.url, 'callback');
}
}
Using the HttpClientTestingModule, I inject the HttpTestingController so I can mock and flush my JSONP HTTP request.
example.service.spec.ts
import { TestBed, inject } from '@angular/core/testing';
import {
HttpClientTestingModule,
HttpTestingController
} from '@angular/common/http/testing';
import { ExampleService } from './example.service';
describe('ExampleService', () => {
let service: ExampleService;
let httpMock: HttpTestingController;
beforeEach(() => {
TestBed.configureTestingModule({
imports: [HttpClientTestingModule],
providers: [ExampleService]
});
service = TestBed.get(ExampleService);
httpMock = TestBed.get(HttpTestingController);
});
describe('#getData', () => {
it('should return an Observable<any>', () => {
const dummyData = { id: 1 };
service.getData().subscribe(data => {
expect(data).toEqual(dummyData);
});
const req = httpMock.expectOne(service.url); // Error
expect(req.request.method).toBe('JSONP');
req.flush(dummyData);
});
});
});
In the end, I get the error
Error: Expected one matching request for criteria "Match URL: https://archive.org/index.php?output=json&callback=callback", found none.
If I change the request method to GET, this test works as expected.
From what I can tell, the HttpClientTestingModule uses the HttpClientTestingBackend but there is no JsonpClientTestingBackend or corresponding interceptor.
How do I test a JSONP HTTP request in Angular?
According to an Angular developer this is a bug. Here's a workaround for now.
example.service.spec.ts
import { TestBed, inject } from '@angular/core/testing';
// Import the HttpClientJsonpModule, HttpBackend, and JsonpClientBackend
import { HttpClientJsonpModule, HttpBackend, JsonpClientBackend } from '@angular/common/http';
import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
import { ExampleService } from './example.service';
describe('ExampleService', () => {
let service: ExampleService;
let httpMock: HttpTestingController;
beforeEach(() => {
TestBed.configureTestingModule({
imports: [HttpClientTestingModule],
// Use the HttpBackend instead of the JsonpClientBackend
providers: [ExampleService, { provide: JsonpClientBackend, useExisting: HttpBackend }]
});
service = TestBed.get(ExampleService);
httpMock = TestBed.get(HttpTestingController);
});
describe('#getData', () => {
it('should return an Observable<any>', () => {
const dummyData = { id: 1 };
service.getData().subscribe(data => {
expect(data).toEqual(dummyData);
});
// Pass a function to the expectOne method
const req = httpMock.expectOne(request => request.url === service.url);
expect(req.request.method).toBe('JSONP');
req.flush(dummyData);
});
});
});