Angular 6 - NullInjectorError: No provider for HttpClient in unit tests

I am importing and using HttpClient in a service as follows:

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable({
providedIn: 'root',
})
export class MyService {
constructor(private http: HttpClient) { }

getData() {
return this.http.get("url...");
}
}


However, when I run ng test for my unit tests, and when those tests use the service, I am getting the error:

Error: StaticInjectorError(DynamicTestModule)[HttpClient]:
StaticInjectorError(Platform: core)[HttpClient]:
NullInjectorError: No provider for HttpClient!


The Angular 6 documentation on HTTP just says to do what I did above.

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