Testing routing and navigation in Angular - Mini Project: Build & Apply

Testing routing and navigation

📖 Scenario: You are building a simple Angular app with two pages: Home and About. You want to test that navigation between these pages works correctly.

🎯 Goal: Create a basic Angular routing setup with two routes, then write a test to check navigation from Home to About page.

📋 What You'll Learn

Create a standalone Angular component called HomeComponent with text 'Home Page'.

Create a standalone Angular component called AboutComponent with text 'About Page'.

Set up Angular routes for path '' to HomeComponent and path 'about' to AboutComponent.

Write a test that navigates from '' to 'about' and verifies the displayed text changes accordingly.

💡 Why This Matters

🌍 Real World

Routing is essential in Angular apps to switch views without reloading the page. Testing routing ensures users can navigate smoothly.

💼 Career

Many Angular developer roles require writing tests for routing to maintain app quality and prevent navigation bugs.

1

Create HomeComponent and AboutComponent

Create two standalone Angular components: HomeComponent that displays the text 'Home Page' inside a <h1> tag, and AboutComponent that displays the text 'About Page' inside a <h1> tag.

Angular

// Create HomeComponent
// Create AboutComponent

Hint

Use @Component decorator with standalone: true and simple templates.

2

Set up Angular routes

Create a constant called appRoutes that is an array of routes. Add a route with path '' that loads HomeComponent, and a route with path 'about' that loads AboutComponent.

Angular

import { Routes } from '@angular/router';

// Create appRoutes array with two routes
// Your code here

Hint

Use Routes type and create an array with two route objects.

3

Configure RouterTestingModule with routes

In your test file, import RouterTestingModule and configure it with appRoutes. Create a test component that uses <router-outlet> to display routed components.

Angular

import { RouterTestingModule } from '@angular/router/testing';
import { Component } from '@angular/core';

@Component({
  selector: 'app-test',
  standalone: true,
  imports: [RouterTestingModule.withRoutes(appRoutes)],
  template: ``
})
export class TestAppComponent {}

// Your test setup code here

Hint

Use RouterTestingModule.withRoutes(appRoutes) in the imports array of the test component.

4

Write a test to navigate and verify page content

Write a test that uses Angular's Router to navigate from the empty path '' to 'about'. Use fixture.detectChanges() and await router.navigate(['about']). Verify that the rendered text contains 'About Page'.

Angular

describe('Routing Test', () => {
  let fixture: ComponentFixture;
  let router: Router;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [TestAppComponent]
    });
    router = TestBed.inject(Router);
    fixture = TestBed.createComponent(TestAppComponent);
    fixture.detectChanges();
  });

  it('should navigate to About page', async () => {
    // Your code here
  });
});

Hint

Use await router.navigate(['about']) and then check the DOM text content.

Practice

1. What is the main purpose of using RouterTestingModule in Angular tests?

easy

A. To style the router links in the application

B. To disable routing completely in tests

C. To create real HTTP requests during navigation

D. To simulate routing behavior without starting the full app

Solution

1. Step 1: Understand the role of RouterTestingModule

   RouterTestingModule is designed to simulate routing in tests without launching the full Angular app.

2. Step 2: Compare options with this purpose

   Styling the router links is incorrect. Creating real HTTP requests during navigation is wrong. Disabling routing completely is incorrect. Simulating routing behavior without starting the full app correctly describes this testing utility.

3. Final Answer:

   To simulate routing behavior without starting the full app -> Option D

4. Quick Check:

   RouterTestingModule simulates routing [OK]

Hint: RouterTestingModule simulates routes in tests, not real navigation [OK]

Common Mistakes:

• Thinking RouterTestingModule styles links
• Assuming it sends real HTTP requests
• Believing it disables routing

2. Which of the following is the correct way to import RouterTestingModule in an Angular test file?

easy

A. import { RouterTestingModule } from '@angular/router/testing';

B. import { RouterTestingModule } from '@angular/core/testing';

C. import { RouterTestingModule } from '@angular/router';

D. import { RouterTestingModule } from '@angular/testing/router';

Solution

1. Step 1: Recall the correct import path

   The RouterTestingModule is provided by the '@angular/router/testing' package.

2. Step 2: Verify each option's path

   Only import { RouterTestingModule } from '@angular/router/testing'; uses the correct path '@angular/router/testing'. Others are incorrect or do not exist.

3. Final Answer:

   import { RouterTestingModule } from '@angular/router/testing'; -> Option A

4. Quick Check:

   Correct import path is '@angular/router/testing' [OK]

Hint: RouterTestingModule always imports from '@angular/router/testing' [OK]

Common Mistakes:

• Importing from '@angular/core/testing'
• Importing from '@angular/router'
• Using a non-existent path

3. Given this test snippet, what will location.path() return after navigation?

const fixture = TestBed.createComponent(AppComponent);
const router = TestBed.inject(Router);
const location = TestBed.inject(Location);
router.navigate(['/dashboard']);
fixture.detectChanges();
await fixture.whenStable();
console.log(location.path());

medium

A. "/"

B. "/dashboard"

C. "/home"

D. "undefined"

Solution

1. Step 1: Understand navigation and location.path()

   Calling router.navigate(['/dashboard']) changes the URL path to '/dashboard'. The Location service reflects this path.

2. Step 2: Confirm location.path() after navigation

   After navigation and stabilization, location.path() returns the current URL path, which is '/dashboard'.

3. Final Answer:

   "/dashboard" -> Option B

4. Quick Check:

   location.path() shows current URL path [OK]

Hint: location.path() returns the current URL after navigation [OK]

Common Mistakes:

• Expecting location.path() to be '/' by default
• Confusing location.path() with component state
• Not awaiting navigation completion

4. Identify the error in this test setup for routing:

beforeEach(() => {
  TestBed.configureTestingModule({
    imports: [RouterTestingModule],
    declarations: [AppComponent]
  });
  router = TestBed.inject(Router);
  location = TestBed.inject(Location);
  fixture = TestBed.createComponent(AppComponent);
  router.navigate(['/profile']);
  fixture.detectChanges();
});

medium

A. router.navigate() must be called after fixture.detectChanges()

B. RouterTestingModule should not be imported in tests

C. Missing call to compileComponents() before creating the component

D. Location service cannot be injected in tests

Solution

1. Step 1: Check Angular test setup best practices

   When using TestBed with components, compileComponents() must be called to compile templates before creating components.

2. Step 2: Analyze the given code

   The code configures the module but does not call compileComponents(), which can cause errors when creating the component.

3. Final Answer:

   Missing call to compileComponents() before creating the component -> Option C

4. Quick Check:

   Always call compileComponents() before createComponent() [OK]

Hint: Always call compileComponents() before createComponent() in tests [OK]

Common Mistakes:

• Skipping compileComponents() causes template errors
• Thinking RouterTestingModule is not needed
• Calling navigate() before detectChanges() is allowed

5. You want to test that navigating to /settings loads the SettingsComponent. Which approach correctly tests this behavior?

hard

A. Use RouterTestingModule with routes, navigate to '/settings', then check if the component instance is of type SettingsComponent

B. Manually create SettingsComponent and call its ngOnInit without routing

C. Use RouterTestingModule but do not define routes, then navigate to '/settings'

D. Navigate to '/settings' without RouterTestingModule and check the URL

Solution

1. Step 1: Set up RouterTestingModule with route definitions

   To test navigation, RouterTestingModule must be configured with routes linking '/settings' to SettingsComponent.

2. Step 2: Navigate to '/settings' and verify component

   After navigation, verify the loaded component instance is SettingsComponent to confirm correct routing.

3. Final Answer:

   Use RouterTestingModule with routes, navigate to '/settings', then check if the component instance is of type SettingsComponent -> Option A

4. Quick Check:

   Define routes and check component after navigation [OK]

Hint: Define routes in RouterTestingModule to test navigation and component loading [OK]

Common Mistakes:

• Not defining routes in RouterTestingModule
• Testing component without routing
• Checking URL without verifying component