To write a unit test in Angular for an input of type number
that handles keydown
events (for ArrowUp
and ArrowDown
), you can use Angular’s TestBed
and fakeAsync
utilities with dispatchEvent
to simulate these events.
Here’s an example of how you can create a test for an HTML input of type number
that increments or decrements its value based on arrow key presses:
HTML (input.component.html
)
<input type="number" id="numberInput" [(ngModel)]="inputValue" (keydown)="onKeyDown($event)" />
TypeScript (input.component.ts
)
import { Component } from '@angular/core';
@Component({
selector: 'app-input',
templateUrl: './input.component.html',
})
export class InputComponent {
inputValue: number = 0; onKeyDown(event: KeyboardEvent): void {
const incrementValue = 1; // Or set it to any number you want for increment/decrement.
if (event.key === 'ArrowUp') {
this.inputValue += incrementValue;
} else if (event.key === 'ArrowDown') {
this.inputValue -= incrementValue;
}
}
}
Unit Test (input.component.spec.ts
)
import { ComponentFixture, TestBed } from '@angular/core/testing';
import { FormsModule } from '@angular/forms';
import { InputComponent } from './input.component';
import { By } from '@angular/platform-browser';
describe('InputComponent', () => {
let component: InputComponent;
let fixture: ComponentFixture<InputComponent>;
let inputElement: HTMLInputElement; beforeEach(async () => {
await TestBed.configureTestingModule({
declarations: [InputComponent],
imports: [FormsModule],
}).compileComponents(); fixture = TestBed.createComponent(InputComponent);
component = fixture.componentInstance;
fixture.detectChanges(); inputElement = fixture.debugElement.query(By.css('#numberInput')).nativeElement;
}); it('should increment the value when ArrowUp is pressed', fakeAsync(() => {
// Initial value should be 0
expect(component.inputValue).toBe(0); // Simulate ArrowUp key press
const event = new KeyboardEvent('keydown', { key: 'ArrowUp' });
inputElement.dispatchEvent(event);
fixture.detectChanges(); // After ArrowUp key press, value should increment by 1
expect(component.inputValue).toBe(1);
})); it('should decrement the value when ArrowDown is pressed', fakeAsync(() => {
// Set initial value to 10
component.inputValue = 10;
fixture.detectChanges(); // Simulate ArrowDown key press
const event = new KeyboardEvent('keydown', { key: 'ArrowDown' });
inputElement.dispatchEvent(event);
fixture.detectChanges(); // After ArrowDown key press, value should decrement by 1
expect(component.inputValue).toBe(9);
}));
});
Explanation:
- Component Setup: The
InputComponent
has an input field bound to a variableinputValue
, and theonKeyDown
function updates the value when theArrowUp
orArrowDown
keys are pressed. - TestBed Setup: The
FormsModule
is imported because of[(ngModel)]
. - Unit Tests:
- The first test simulates pressing the
ArrowUp
key and checks if the value increments. - The second test simulates pressing the
ArrowDown
key and verifies that the value decrements.