ngSubmit won't fire when clicking the submit button with Jasmine

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06-09-2024

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ngSubmit Won't Fire When Clicking the Submit Button with Jasmine: A Solution and Explanation

This article delves into a common issue encountered when testing Angular forms using Jasmine: the ngSubmit directive not firing when clicking the submit button. We'll analyze the problem, provide a solution, and offer insights to enhance your understanding of Angular testing.

The Problem:

As described in the Stack Overflow question, the submit() function is correctly called when using a (click) event on the submit button but fails when utilizing ngSubmit within the form. This discrepancy is a result of how Angular handles form submissions and the way Jasmine simulates user interactions.

Solution:

The key to resolving this lies in understanding that ngSubmit is triggered by the form's submission event, not directly by clicking the button. To simulate this in your Jasmine test, you need to trigger the form's submit event instead of directly clicking the button. Here's how you can achieve this:

it('should call the submit method', () => {
  let debugElement = _fixture.debugElement;
  let form = debugElement.query(By.css('form')); // Get the form element

  _fixture.detectChanges();

  // Trigger the form's submit event
  form.triggerEventHandler('submit', null); 

  expect(submitSpy).toHaveBeenCalled();
});

Explanation:

1. form.triggerEventHandler('submit', null): This line triggers the 'submit' event on the form element, simulating the user submitting the form. The null argument represents the event data, which is not relevant in this case.

Additional Insights:

• ngSubmit vs. (click): While both ngSubmit and (click) can be used for form submissions, they have distinct purposes. ngSubmit is designed for handling form submission events, while (click) is a more general event listener for button clicks. ngSubmit often offers better integration with Angular's form validation and data binding capabilities.
• Testing Form Submission: The approach outlined above is crucial for testing the submission logic of your Angular forms. It ensures that your test simulates the actual user interaction and verifies that the intended functionality is triggered upon form submission.
• Complete Example: To illustrate the solution, consider this complete example:

<form (ngSubmit)="submit()" #addPersonForm="ngForm">
    <button class="add-button" type="submit" tabindex="5">Add Person</button>
</form>

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

// Your component under test
@Component({
  selector: 'app-my-form',
  template: `
    <form (ngSubmit)="submit()" #addPersonForm="ngForm">
        <button class="add-button" type="submit" tabindex="5">Add Person</button>
    </form>
  `,
})
class MyFormComponent {
  submit() {
    // Your form submission logic here
  }
}

describe('MyFormComponent', () => {
  let component: MyFormComponent;
  let fixture: ComponentFixture<MyFormComponent>;
  let submitSpy: jasmine.Spy;

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      declarations: [MyFormComponent],
    }).compileComponents();
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(MyFormComponent);
    component = fixture.componentInstance;
    submitSpy = spyOn(component, 'submit'); // Create a spy on the submit method
    fixture.detectChanges();
  });

  it('should call the submit method', () => {
    let debugElement = fixture.debugElement;
    let form = debugElement.query(By.css('form')); // Get the form element

    fixture.detectChanges();

    // Trigger the form's submit event
    form.triggerEventHandler('submit', null); 

    expect(submitSpy).toHaveBeenCalled();
  });
});

By following this solution and understanding the underlying concepts, you can confidently write effective unit tests for your Angular forms using Jasmine.

Attribution:

This article is based on the Stack Overflow question titled "ngSubmit won't fire when clicking the submit button with Jasmine" by user [user_name] (https://stackoverflow.com/questions/46353175/ngsubmit-wont-fire-when-clicking-the-submit-button-with-jasmine).