Adding validators in angular forms

Your issue comes from the fact that you don't do things in order and don't rely on the framework to make your tests.

I made a sandbox with a working test, feel free to look at it. Now for the explanation :

Let's start with the component :

@Component({
  selector: 'hello',
  template: `
  <form #myForm="ngForm">
    <input type="text" maxlength="20" name="patient" id="patient" [(ngModel)]="patient">
  </form>
  `,
  styles: [`h1 { font-family: Lato; }`]
})
export class HelloComponent  {
  @ViewChild('myForm') myForm: NgForm;
  patient: string;
}

A very simple component with a template driven form and a basic validation and binding.

If you do this

ngOnInit() {
  console.log(this.myForm.controls);
  setTimeout(() => console.log(this.myForm.controls));
}

You will see both undefined and { patient: FormControl }. This happens because you don't wait for the view to be initialized before doing your tests. This means that the test can't find the form control, and hence can't pass.

Now for the test itself :

import { Component } from '@angular/core';
import { ComponentFixture, TestBed, async } from '@angular/core/testing';
import { By } from '@angular/platform-browser';

import { HelloComponent } from './hello.component';

import { FormsModule } from '@angular/forms';

describe('HelloComponent', () => {
  let fixture: ComponentFixture<HelloComponent>;
  let component: HelloComponent;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [FormsModule],
      declarations: [HelloComponent]
    });

    fixture = TestBed.createComponent(HelloComponent);
    component = fixture.debugElement.children[0].componentInstance;

    fixture.detectChanges();
  });

  it('should be invalid with more than 20 chars', async(() => {
    setTimeout(() => {
      component.myForm.controls['patient'].setValue('ddddddddddddddddddddd'); // 21
      fixture.detectChanges();
      expect(component.myForm.control.invalid).toEqual(true);
    });
  }));
});

the start is very basic, test bed is configured and changes are detected.

Now comes the part where you test : you first must wait for the component to load with a timeout, then, you need to set the value on the form by using the framework :

component.myForm.controls['patient'].setValue('ddddddddddddddddddddd'); // 21

This inputs 21 d into the input, which is making it invalid. After that, you need to trigger the changes detection, and now you can make your expectation with

expect(component.myForm.control.invalid).toEqual(true);

This will take the form as a control, meaning it has all the properties and functions a FormControl has. Among these, you can find the invalid property, which states if your control is in an invalid state.

Again, I have to state that this kind of test is useless, because you basically try to see if the Framework is working properly. That's not your job, that's Angular team's job. If you want to test something, you should test that the form can't be submitted when it has an invalid state, which is a business rule (I guess) and prevents side effects (unlike this test).