Answers for "NullInjectorError: R3InjectorError(DynamicTestModule)[CurrencyExchangeRateService -> HttpClient -> HttpClient]: NullInjectorError: No provider for HttpClient!"

angular No provider for HttpClient

// open the root app.module.ts,
import { HttpClientModule } from '@angular/common/http';

// add it to the @NgModule.imports array.
imports:[HttpClientModule,  ]

NullInjectorError: No provider for HttpClient!

@NgModule({
...
imports:[ HttpClientModule ]
...
})