app.module.ts

...

 import config from './../../config.json';
+import { BlubDirective } from './blub.directive';

 // App Setup
 @NgModule({
-  declarations: [AppComponent],
+  declarations: [AppComponent, BlubDirective],
   entryComponents: [],

...

blub.directive.spec.ts

import { BlubDirective } from './blub.directive';

describe('BlubDirective', () => {
  it('should create an instance', () => {
    const directive = new BlubDirective();
    expect(directive).toBeTruthy();
  });
});

blub.directive.ts

import { Directive } from '@angular/core';

@Directive({
  selector: '[appBlub]'
})
export class BlubDirective {

  constructor() { }

}