Angular 2 Custom validation unit testing

What you need to do is get the injector that has the NgForm. It took me a while to figure it out. I thought you could just get it from the debugElement, but it looks like you need to get it from it's child¹.

let form: NgForm = fixture.debugElement.children[0].injector.get(NgForm);

The you can just get individual controls from the form group with

let emailControl = form.control.get('email');
expect(emailControl.valid).toBe(true);

Or you can just check the form for a specific error

expect(form.control.hasError('emailInvalid', ['email'])).toBe(true);

Below is a complete test

import { Component, forwardRef, Directive } from '@angular/core';
import { TestBed, getTestBed, async } from '@angular/core/testing';
import { FormsModule, NG_VALIDATORS, Validator, AbstractControl, NgForm } from '@angular/forms';
import { dispatchEvent } from '@angular/platform-browser/testing/browser_util';
import { By } from '@angular/platform-browser';

@Directive({
  selector: '[ngModel][validEmail]',
  providers: [
    {
      provide: NG_VALIDATORS,
      useExisting: forwardRef(() => EmailValidatorDirective),
      multi: true
    }
  ]
})
class EmailValidatorDirective implements Validator {

  validate(c: AbstractControl): { [key: string]: any } {
    if (c.value !== '[email protected]') {
      return { notPeeskillet: true };
    }
    return null;
  }
}

@Component({
  template: `
    <form>
      <input name="email" [ngModel]="email" validEmail />
    </form>
  `
})
class TestComponent {
  email;
}

describe('component: TestComponent', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [FormsModule],
      declarations: [TestComponent, EmailValidatorDirective]
    });
  });

  it('should validate', async(() => {
    let fixture = TestBed.createComponent(TestComponent);
    let comp = fixture.componentInstance;
    let debug = fixture.debugElement;
    let input = debug.query(By.css('[name=email]'));

    fixture.detectChanges();
    fixture.whenStable().then(() => {
      input.nativeElement.value = '[email protected]';
      dispatchEvent(input.nativeElement, 'input');
      fixture.detectChanges();

      let form: NgForm = debug.children[0].injector.get(NgForm);
      let control = form.control.get('email');
      expect(control.hasError('notPeeskillet')).toBe(true);
      expect(form.control.valid).toEqual(false);
      expect(form.control.hasError('notPeeskillet', ['email'])).toEqual(true);

      input.nativeElement.value = '[email protected]';
      dispatchEvent(input.nativeElement, 'input');
      fixture.detectChanges();

      expect(control.hasError('notPeeskillet')).toBe(false);
      expect(form.control.valid).toEqual(true);
      expect(form.control.hasError('notPeeskillet', ['email'])).toEqual(false);
    });
  }));
});

---

_{1 - Found it in the source code tests}

The above best answer didn't work for me but I was able to test my custom validator in the following way:

const associateRateControl = component.distributionSettingsForm.controls['associateRate'];
associateRateControl.setValue('plus ultra');
fixture.detectChanges();
expect(component.distributionSettingsForm.hasError('noCatalog')).toEqual(true);