docs: add http guide sample and adjust text (#21326)

PR Close #21326

aio/content/examples/http/src/testing/global-jasmine.ts

@@ -0,0 +1,3 @@
+import jasmineRequire from 'jasmine-core/lib/jasmine-core/jasmine.js';
+
+window['jasmineRequire'] = jasmineRequire;

aio/content/examples/http/src/testing/http-client.spec.ts

@@ -0,0 +1,192 @@
+// #docplaster
+// #docregion imports
+// Http testing module and mocking controller
+import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
+
+// Other imports
+import { TestBed } from '@angular/core/testing';
+import { HttpClient, HttpErrorResponse } from '@angular/common/http';
+
+// #enddocregion imports
+import { HttpHeaders } from '@angular/common/http';
+
+interface Data {
+  name: string;
+}
+
+const testUrl = '/data';
+
+// #docregion setup
+describe('HttpClient testing', () => {
+  let httpClient: HttpClient;
+  let httpTestingController: HttpTestingController;
+
+  beforeEach(() => {
+    TestBed.configureTestingModule({
+      imports: [ HttpClientTestingModule ]
+    });
+
+    // Inject the http service and test controller for each test
+    httpClient = TestBed.get(HttpClient);
+    httpTestingController = TestBed.get(HttpTestingController);
+  });
+  // #enddocregion setup
+  // #docregion afterEach
+  afterEach(() => {
+    // After every test, assert that there are no more pending requests.
+    httpTestingController.verify();
+  });
+  // #enddocregion afterEach
+  // #docregion setup
+  /// Tests begin ///
+  // #enddocregion setup
+  // #docregion get-test
+  it('can test HttpClient.get', () => {
+    const testData: Data = {name: 'Test Data'};
+
+    // Make an HTTP GET request
+    httpClient.get<Data>(testUrl)
+      .subscribe(data =>
+        // When observable resolves, result should match test data
+        expect(data).toEqual(testData)
+      );
+
+    // The following `expectOne()` will match the request's URL.
+    // If no requests or multiple requests matched that URL
+    // `expectOne()` would throw.
+    const req = httpTestingController.expectOne('/data');
+
+    // Assert that the request is a GET.
+    expect(req.request.method).toEqual('GET');
+
+    // Respond with mock data, causing Observable to resolve.
+    // Subscribe callback asserts that correct data was returned.
+    req.flush(testData);
+
+    // Finally, assert that there are no outstanding requests.
+    httpTestingController.verify();
+  });
+  // #enddocregion get-test
+  it('can test HttpClient.get with matching header', () => {
+    const testData: Data = {name: 'Test Data'};
+
+    // Make an HTTP GET request with specific header
+    httpClient.get<Data>(testUrl, {
+        headers: new HttpHeaders({'Authorization': 'my-auth-token'})
+      })
+      .subscribe(data =>
+        expect(data).toEqual(testData)
+      );
+
+      // Find request with a predicate function.
+    // #docregion predicate
+    // Expect one request with an authorization header
+    const req = httpTestingController.expectOne(
+      req => req.headers.has('Authorization')
+    );
+    // #enddocregion predicate
+    req.flush(testData);
+  });
+
+  it('can test multiple requests', () => {
+    let testData: Data[] = [
+      { name: 'bob' }, { name: 'carol' },
+      { name: 'ted' }, { name: 'alice' }
+    ];
+
+    // Make three requests in a row
+    httpClient.get<Data[]>(testUrl)
+      .subscribe(d => expect(d.length).toEqual(0, 'should have no data'));
+
+    httpClient.get<Data[]>(testUrl)
+      .subscribe(d => expect(d).toEqual([testData[0]], 'should be one element array'));
+
+    httpClient.get<Data[]>(testUrl)
+      .subscribe(d => expect(d).toEqual(testData, 'should be expected data'));
+
+    // #docregion multi-request
+    // get all pending requests that match the given URL
+    const requests = httpTestingController.match(testUrl);
+    expect(requests.length).toEqual(3);
+
+    // Respond to each request with different results
+    requests[0].flush([]);
+    requests[1].flush([testData[0]]);
+    requests[2].flush(testData);
+    // #enddocregion multi-request
+  });
+
+  // #docregion 404
+  it('can test for 404 error', () => {
+    const emsg = 'deliberate 404 error';
+
+    httpClient.get<Data[]>(testUrl).subscribe(
+      data => fail('should have failed with the 404 error'),
+      (error: HttpErrorResponse) => {
+        expect(error.status).toEqual(404, 'status');
+        expect(error.error).toEqual(emsg, 'message');
+      }
+    );
+
+    const req = httpTestingController.expectOne(testUrl);
+
+    // Respond with mock error
+    req.flush(emsg, { status: 404, statusText: 'Not Found' });
+  });
+  // #enddocregion 404
+
+  // #docregion network-error
+  it('can test for network error', () => {
+    const emsg = 'simulated network error';
+
+    httpClient.get<Data[]>(testUrl).subscribe(
+      data => fail('should have failed with the network error'),
+      (error: HttpErrorResponse) => {
+        expect(error.error.message).toEqual(emsg, 'message');
+      }
+    );
+
+    const req = httpTestingController.expectOne(testUrl);
+
+    // Create mock ErrorEvent, raised when something goes wrong at the network level.
+    // Connection timeout, DNS error, offline, etc
+    const errorEvent = new ErrorEvent('so sad', {
+      message: emsg,
+      // #enddocregion network-error
+      // The rest of this is optional and not used.
+      // Just showing that you could provide this too.
+      filename: 'HeroService.ts',
+      lineno: 42,
+      colno: 21
+    // #docregion network-error
+    });
+
+    // Respond with mock error
+    req.error(errorEvent);
+  });
+  // #enddocregion network-error
+
+  it('httpTestingController.verify should fail if HTTP response not simulated', () => {
+    // Sends request
+    httpClient.get('some/api').subscribe();
+
+    // verify() should fail because haven't handled the pending request.
+    expect(() => httpTestingController.verify()).toThrow();
+
+    // Now get and flush the request so that afterEach() doesn't fail
+    const req = httpTestingController.expectOne('some/api');
+    req.flush(null);
+  });
+
+  // Proves that verify in afterEach() really would catch error
+  // if test doesn't simulate the HTTP response.
+  //
+  // Must disable this test because can't catch an error in an afterEach().
+  // Uncomment if you want to confirm that afterEach() does the job.
+  // it('afterEach() should fail when HTTP response not simulated',() => {
+  //   // Sends request which is never handled by this test
+  //   httpClient.get('some/api').subscribe();
+  // });
+// #docregion setup
+});
+// #enddocregion setup