Directive unit testing fails - jestjs

Question

I am using jest.js for testing with my angular app. here is the directive I use in html:
<textarea errorHighlighter formControlName="Url" name="Url" cols="50" rows="5"
placeholder="Enter Page URL" (ngModelChange)="pageUrlChanges($event)"></textarea>
here is my directive.ts file:
import { Directive, ElementRef, SimpleChanges, HostListener, Renderer2 } from '#angular/core';
import { NgControl } from '#angular/forms';
#Directive({
selector: '[errorHighlighter]'
})
export class ErrorHighlighterDirective {
constructor(private el: ElementRef, private control: NgControl, private renderer: Renderer2) { }
#HostListener('input') oninput() {
if (this.el.nativeElement && this.control) {
if (this.control.control.status === 'INVALID') {
this.renderer.addClass(this.el.nativeElement, 'has-err');
} else {
this.renderer.removeClass(this.el.nativeElement, 'has-err');
}
}
}
}
this is written to show the error border around the input field. I am trying to test the same like this:
import { ErrorHighlighterDirective } from './error-highlighter.directive';
import { Directive, ElementRef, SimpleChanges, HostListener, Renderer2, Component, DebugElement } from '#angular/core';
import { NgControl, FormGroup, FormsModule, FormControl, ReactiveFormsModule } from '#angular/forms';
import { TestBed, ComponentFixture } from '#angular/core/testing';
#Component({
template: `<input errorHighlighter formControlName="Url" type="text">`
})
class TestHighlighterComponent { }
describe('ErrorHighlighterDirective', () => {
let component: TestHighlighterComponent;
let fixture: ComponentFixture<TestHighlighterComponent>;
let inputEl: DebugElement;
const fg: FormGroup = new FormGroup({
'Url': new FormControl('')
});
beforeEach(() => {
TestBed.configureTestingModule({
declarations: [TestHighlighterComponent, ErrorHighlighterDirective],
imports: [FormsModule, ReactiveFormsModule],
providers: [
{ provide: NgControl, useValue: fg }
]
});
fixture = TestBed.createComponent(TestHighlighterComponent);
component = fixture.componentInstance;
inputEl = fixture.debugElement.query(By.css('input'));
});
it('should create an instance', () => {
const directive = new ErrorHighlighterDirective(inputEl, fg, Renderer2);
expect(directive).toBeTruthy();
});
});
But the test not succeeds. getting error like below:
● Test suite failed to run
TypeScript diagnostics (customize using `[jest-config].globals.ts-jest.diagnostics` option):
src/app/directives/error-highlighter.directive.spec.ts:33:46 - error TS2304: Cannot find name 'By'.
33 inputEl = fixture.debugElement.query(By.css('input'));
~~
src/app/directives/error-highlighter.directive.spec.ts:38:66 - error TS2345: Argument of type 'FormGroup' is not assignable to parameter of type 'NgControl'.
Type 'FormGroup' is missing the following properties from type 'NgControl': name, valueAccessor, viewToModelUpdate, control, path
38 const directive = new ErrorHighlighterDirective(inputEl, fg, Renderer2);
Any one help me to understand and fix these issue? I am not much familiar with angular test either jest.js.

Answer 1

You can use By.directive
e.g.
const directiveEl = fixture.debugElement.query(By.directive(MyDirective));
expect(directiveEl).not.toBeNull();
You need to import By from angular.platform-browser
import { By } from '#angular/platform-browser
You can further read here.
You can use any selector By.css that you can use with css. And a selector for a class is simply .classname.
e.g.
By.css(.classname)
or
By.css('input[type=radio]')
or
By.css('textarea')