How to unit test ngx-formly?

I am trying to unit test ngx formly but I am getting the following error:

[Formly Error] The validator "emailValidator" could not be found. Please make sure that is registered through the FormlyModule declaration.

I also checked the angular formly documentation and they have written the code in the same way.

Documentation:

FIELD WITH CUSTOM VALIDATION
You just need to include the name of the validate function, declared in FormlyModule, within the property validators.validation.

{
  key: 'ip',
  type: 'input',
  templateOptions: {
    label: 'IP Address (using custom validation declared in ngModule)',
    required: true,
  },
  validators: {
    validation: ['ip'],
  },
},

Documentation Link: https://formly.dev/guide/validation

** MY CODE **

form.component.ts:

export class FormComponent {
  fields: FormlyFieldConfig[] = [
    {
      key: 'email',
      type: 'input',
      templateOptions: {
        label: 'Email address',
        placeholder: 'Enter email',
        type: 'email',
        required: true,
        attributes: {
          autocapitalize: 'off',
          autocorrect: 'off',
          autocomplete: 'off',
        },
      },
      validators: {
        validation: ['emailValidator'],
      },
    },
  ];

form.component.spec.ts:

import { ComponentFixture, TestBed } from '@angular/core/testing';
import { ReactiveFormsModule } from '@angular/forms';
import { FormlyModule } from '@ngx-formly/core';
import { FormlyMaterialModule } from '@ngx-formly/material';

import { FormComponent } from './form.component';

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

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      declarations: [ FormComponent],
      imports: [
        FormlyModule.forRoot(),
        FormlyMaterialModule,
        ReactiveFormsModule,
      ]
    })
    .compileComponents();
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(FormComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
  });

});

Can someone please guide me? Any leads would be helpful! Thank you!

can you please share your App.module file content? Your "emailValidator" has to be registered in your import section of app.module file in the following way:

imports: [
FormlyModule.forRoot({
   validators: [
                { name: 'emailvalidator', validation: validator_function_name },
               
              ]
           )}

please check here https://formly.dev/examples/validation/custom-validation