docs: update HTTP testing setup guidance

Update testing documentation clarify HttpClient testing providers

Fixed angular#68792

Author: aparzi

adev/src/content/guide/http/testing.md

@@ -8,15 +8,12 @@ Finally, tests can verify that the app made no unexpected requests.
 
 ## Setup for testing
 
-To begin testing usage of `HttpClient`, configure `TestBed` and include `provideHttpClient()` and `provideHttpClientTesting()` in your test's setup. This configures `HttpClient` to use a test backend instead of the real network. It also provides `HttpTestingController`, which you'll use to interact with the test backend, set expectations about which requests have been made, and flush responses to those requests. `HttpTestingController` can be injected from `TestBed` once configured.
-
-IMPORTANT: Keep in mind to provide `provideHttpClient()` **before** `provideHttpClientTesting()`, as `provideHttpClientTesting()` will overwrite parts of `provideHttpClient()`. Doing it the other way around can potentially break your tests.
+To begin testing usage of `HttpClient`, configure `TestBed` and include `provideHttpClientTesting()` in your test's setup. `HttpClient` is provided by Angular's test environment, and `provideHttpClientTesting()` configures it to use a test backend instead of the real network. It also provides `HttpTestingController`, which you'll use to interact with the test backend, set expectations about which requests have been made, and flush responses to those requests. `HttpTestingController` can be injected from `TestBed` once configured.
 
 ```ts
 TestBed.configureTestingModule({
   providers: [
     // ... other test providers
-    provideHttpClient(),
     provideHttpClientTesting(),
   ],
 });
@@ -26,13 +23,24 @@ const httpTesting = TestBed.inject(HttpTestingController);
 
 Now when your tests make requests, they will hit the testing backend instead of the normal one. You can use `httpTesting` to make assertions about those requests.
 
+### Configuring `HttpClient` in tests
+
+If a test needs to configure `HttpClient` features, such as interceptors, include `provideHttpClient(...)` before `provideHttpClientTesting()`.
+IMPORTANT: Keep in mind to provide `provideHttpClient()` **before** `provideHttpClientTesting()`, as `provideHttpClientTesting()` will overwrite parts of `provideHttpClient()`. Doing it the other way around can potentially break your tests.
+
+```ts
+TestBed.configureTestingModule({
+  providers: [provideHttpClient(withInterceptors([authInterceptor])), provideHttpClientTesting()],
+});
+```
+
 ## Expecting and answering requests
 
 For example, you can write a test that expects a GET request to occur and provides a mock response:
 
 ```ts
 TestBed.configureTestingModule({
-  providers: [ConfigService, provideHttpClient(), provideHttpClientTesting()],
+  providers: [ConfigService, provideHttpClientTesting()],
 });
 
 const httpTesting = TestBed.inject(HttpTestingController);