Q: What is the async pipe and why is it useful?

**Target Audience:** Developers who have written | async in a template and want to know exactly what it does — assumes basic Observables, explains everything else. **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The behaviour below was produced on Angular 22.2.3: templates compiled with ngc (strict templates), run in jsdom, and subscriptions counted with instrumented Observables. The "insid

Question 1

What is Angular and how does it differ from AngularJS?

Accepted Answer

**Target Audience:** Anyone preparing for an Angular interview — assumes basic JavaScript, no Angular or AngularJS required. **Difficulty:** Easy > **How to read this doc:** Ideas are explained in plain language first, then tagged with 📌 Interview term: so you also learn the words an interviewer listens for. The output in section 5 was produced by compiling and running the example on Angular 22.2.3, and the default-behaviour claims in section 6 were read from the Angular 22.2.3 pa

Question 2

What does the Angular CLI provide?

Accepted Answer

**Target Audience:** Anyone preparing for an Angular interview — no Angular experience needed. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Everything under "Verified" was produced by running Angular CLI 22.2.3 in a sandbox: ng new, ng generate --dry-run, ng serve, ng build, ng test and ng lint, with the real output quoted. ng add an

Question 3

What is the fixture.detectChanges() method in Angular testing, and when should you call it?

Accepted Answer

**Target Audience:** Developers writing or reviewing Angular component tests; assumes you have seen a TestBed spec but not much more. **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the vocabulary an interviewer listens for. Every behaviour quoted below was produced by running the spec in the example with Angular CLI 22.2.3 (ng test --watch=false, Vitest + jsdom), in the default zoneles

Question 4

Explain how to perform unit testing on components with Signals using TestBed.

Accepted Answer

**Target Audience:** Developers moving component tests from @Input()/@Output() to the signal APIs (input(), model(), output(), computed(), effect()). **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. All results were produced by running the example spec with Angular CLI 22.2.3 (ng test --watch=false, Vitest, the default zon

Question 5

What is ComponentFixtureAutoDetect and how does it affect unit tests?

Accepted Answer

**Target Audience:** Developers maintaining Angular test suites, especially ones migrating Zone-based specs to a zoneless Angular 22 project. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Two workspaces were used, both on Angular CLI 22.2.3 with Vitest: the default zoneless one from ng new, and a copy that loads zone.js 0.16.3 so the Zone behaviour could be run too. Every behaviour below comes from those runs

Question 6

What is the async pipe and why is it useful?

Accepted Answer

**Target Audience:** Developers who have written | async in a template and want to know exactly what it does — assumes basic Observables, explains everything else. **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The behaviour below was produced on Angular 22.2.3: templates compiled with ngc (strict templates), run in jsdom, and subscriptions counted with instrumented Observables. The "insid

Question 7

Standalone bootstrapApplication — how does Angular bootstrap without NgModules in 2025?

Accepted Answer

**Target Audience:** Developers who can bootstrap an app and now want to explain what happens underneath, for senior interviews or for debugging startup problems. **Difficulty:** Medium to Hard > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The sequence below was read from the installed Angular 22.2.3 source (bootstrapApplication in @angular/platform-browser, internalCreateApplication and bootstrap

Question 8

What do @HostListener and @HostBinding do?

Accepted Answer

**Target Audience:** Developers preparing for an Angular interview who have written a directive and want to change or listen to the element it sits on, and who want to know the modern recommended form. **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every "Verified" block was compiled with ngc (strict templates) on Angular 22.2.3 and run; the HTML is the real outerHTML of the elements. Reco

Question 9

How do you test signal components, defer blocks, and new control flow in 2025?

Accepted Answer

**Target Audience:** Developers testing templates written with the modern Angular syntax: signals, @defer, and built-in control flow. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The title says 2025; everything here was run on the current release, Angular 22.2.3 with CLI 22.2.3 (ng test --watch=false, Vitest + jsdom, zoneless). Deep detail on signal inputs, outputs and effects is on its own page

Question 10

What does ChangeDetectorRef do?

Accepted Answer

**Target Audience:** Developers who know what a component is and want to control when its view updates — no internals knowledge assumed. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the vocabulary an interviewer expects. The method list was read from the Angular 22.2.3 typings, and every DOM snapshot below was produced by compiling and running the example on 22.2.3. ## 1. Why This Even Matters — A Story First Think

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Easy

What is Angular and how does it differ from AngularJS?

What does the Angular CLI provide?

What is the fixture.detectChanges() method in Angular testing, and when should you call it?

Medium

Explain how to perform unit testing on components with Signals using TestBed.

What is ComponentFixtureAutoDetect and how does it affect unit tests?

What is the async pipe and why is it useful?

Standalone bootstrapApplication — how does Angular bootstrap without NgModules in 2025?

What do @HostListener and @HostBinding do?

How do you test signal components, defer blocks, and new control flow in 2025?

Hard

What does ChangeDetectorRef do?

How does change detection work in Angular?

What is Zone.js, how does it monkey-patch browser APIs, and how do you build a Zoneless Angular application?

What is zoneless Angular and how does it improve performance in Angular 18?

What are Angular Signals?

What is NgZone and when do you run outside Angular?

What is the difference between fakeAsync, tick, and waitForAsync in Angular unit tests?