I need to remove unsafe from my url: unsafe:blob:<http://localhost:1234/example>, Below is what I did.

Script: 

```
import {DomSanitizationService} from '@angular/platform-browser';

class example{
  public DomSanitizer: DomSanitizationService;
  public url;

  constructor() {
    this.url = 'www.example.com';
  }
}

```

HTML:

```
<a href={{DomSanitizer.bypassSecurityTrustHtml(url)}}>

```

However, it gives me error: TypeError: Cannot read property 'bypassSecurityTrustHtml' of undefined. I checked DomSanitizationService in @angular/platform-browser, it is an abstract class and cannot be instantiated. What is the right way to call? I saw a lot of answer like this ([How to avoid adding prefix “unsafe” to link by Angular2?](https://stackoverflow.com/questions/37432609/how-to-avoid-adding-prefix-unsafe-to-link-by-angular2)), the DomSanitizationService is passed from constructor but I don't understand when instantiated the class, what should be passed in. Besides, I don't want to change the contract of constructor. I would like to know what is the right way to achieve my goal. I am using angular2.

**Update**:
Now I am able to make it work by injecting DomSanitizationService through constructor, however, in my test,
I need to instantiate my component and what should be passed in for DomSanitizationService?