docs: how to test a http interceptor

README.md

@@ -3342,6 +3342,97 @@ describe('TestHttpRequest', () => {
 
 ---
 
+## How to test a http interceptor
+
+The source file is here:
+[examples/TestHttpInterceptor/test.spec.ts](https://github.com/ike18t/ng-mocks/blob/master/examples/TestHttpInterceptor/test.spec.ts)
+
+```typescript
+import {
+  HTTP_INTERCEPTORS,
+  HttpClient,
+  HttpClientModule,
+  HttpEvent,
+  HttpHandler,
+  HttpInterceptor,
+  HttpRequest,
+} from '@angular/common/http';
+import {
+  HttpClientTestingModule,
+  HttpTestingController,
+} from '@angular/common/http/testing';
+import { Injectable, NgModule } from '@angular/core';
+import { TestBed } from '@angular/core/testing';
+import { MockBuilder } from 'ng-mocks';
+import { Observable } from 'rxjs';
+
+// An interceptor we want to test.
+@Injectable()
+class TargetInterceptor implements HttpInterceptor {
+  protected value = 'HttpInterceptor';
+
+  public intercept(
+    request: HttpRequest<void>,
+    next: HttpHandler
+  ): Observable<HttpEvent<void>> {
+    return next.handle(
+      request.clone({
+        setHeaders: {
+          'My-Custom': this.value,
+        },
+      })
+    );
+  }
+}
+
+// A module with its definition.
+@NgModule({
+  imports: [HttpClientModule],
+  providers: [
+    TargetInterceptor,
+    {
+      multi: true,
+      provide: HTTP_INTERCEPTORS,
+      useClass: TargetInterceptor,
+    },
+  ],
+})
+class TargetModule {}
+
+describe('TestHttpInterceptor', () => {
+  // Because we want to test the interceptor, we pass it as the first
+  // parameter of MockBuilder. To correctly satisfy its dependencies
+  // we need to pass its module as the second parameter. Also we
+  // should mocking HTTP_INTERCEPTORS and replace HttpClientModule
+  // with HttpClientTestingModule.
+  beforeEach(() =>
+    MockBuilder(TargetInterceptor, TargetModule)
+      .keep(HTTP_INTERCEPTORS)
+      .replace(HttpClientModule, HttpClientTestingModule)
+  );
+
+  it('triggers interceptor', () => {
+    const client: HttpClient = TestBed.get(HttpClient);
+    const httpMock: HttpTestingController = TestBed.get(
+      HttpTestingController
+    );
+
+    // Let's do a simply request.
+    client.get('/target').subscribe();
+
+    // Now we can assert that a header has been added to the request.
+    const req = httpMock.expectOne('/target');
+    expect(req.request.headers.get('My-Custom')).toEqual(
+      'HttpInterceptor'
+    );
+    req.flush('');
+    httpMock.verify();
+  });
+});
+```
+
+---
+
 ## Find an issue or have a question or a request?
 
 [Ask a question on gitter](https://gitter.im/ng-mocks/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge),

examples/TestHttpInterceptor/test.spec.ts

@@ -0,0 +1,71 @@
+import {
+  HTTP_INTERCEPTORS,
+  HttpClient,
+  HttpClientModule,
+  HttpEvent,
+  HttpHandler,
+  HttpInterceptor,
+  HttpRequest,
+} from '@angular/common/http';
+import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
+import { Injectable, NgModule } from '@angular/core';
+import { TestBed } from '@angular/core/testing';
+import { MockBuilder } from 'ng-mocks';
+import { Observable } from 'rxjs';
+
+// An interceptor we want to test.
+@Injectable()
+class TargetInterceptor implements HttpInterceptor {
+  protected value = 'HttpInterceptor';
+
+  public intercept(request: HttpRequest<void>, next: HttpHandler): Observable<HttpEvent<void>> {
+    return next.handle(
+      request.clone({
+        setHeaders: {
+          'My-Custom': this.value,
+        },
+      })
+    );
+  }
+}
+
+// A module with its definition.
+@NgModule({
+  imports: [HttpClientModule],
+  providers: [
+    TargetInterceptor,
+    {
+      multi: true,
+      provide: HTTP_INTERCEPTORS,
+      useClass: TargetInterceptor,
+    },
+  ],
+})
+class TargetModule {}
+
+describe('TestHttpInterceptor', () => {
+  // Because we want to test the interceptor, we pass it as the first
+  // parameter of MockBuilder. To correctly satisfy its dependencies
+  // we need to pass its module as the second parameter. Also we
+  // should mocking HTTP_INTERCEPTORS and replace HttpClientModule
+  // with HttpClientTestingModule.
+  beforeEach(() =>
+    MockBuilder(TargetInterceptor, TargetModule)
+      .keep(HTTP_INTERCEPTORS)
+      .replace(HttpClientModule, HttpClientTestingModule)
+  );
+
+  it('triggers interceptor', () => {
+    const client: HttpClient = TestBed.get(HttpClient);
+    const httpMock: HttpTestingController = TestBed.get(HttpTestingController);
+
+    // Let's do a simply request.
+    client.get('/target').subscribe();
+
+    // Now we can assert that a header has been added to the request.
+    const req = httpMock.expectOne('/target');
+    expect(req.request.headers.get('My-Custom')).toEqual('HttpInterceptor');
+    req.flush('');
+    httpMock.verify();
+  });
+});

examples/TestHttpRequest/test.spec.ts

@@ -37,17 +37,17 @@ describe('TestHttpRequest', () => {
   it('sends a request', () => {
     // Let's extract the service and http controller for testing.
     const service: TargetService = TestBed.get(TargetService);
-    const http: HttpTestingController = TestBed.get(HttpTestingController);
+    const httpMock: HttpTestingController = TestBed.get(HttpTestingController);
 
     // A simple subscription to check what the service returns.
     let actual: any;
     service.fetch().subscribe(value => (actual = value));
 
     // Simulating a request.
-    const req = http.expectOne('/data');
+    const req = httpMock.expectOne('/data');
     expect(req.request.method).toEqual('GET');
     req.flush([false, true, false]);
-    http.verify();
+    httpMock.verify();
 
     // Asserting the result.
     expect(actual).toEqual([false, true, false]);