Cannot querySelect input of ion-searchbar in Jasmine tests

I’m running a simple test - enter a value into an ion-searchbar.
In the browser I can run:

document.querySelector('ion-searchbar');  //=> returns search bar OK 
document.querySelector('input');  //=> returns input field OK

In my tests when I try to grab the input the following all fail:

    const el: HTMLElement = fixture.nativeElement;
    const input = el.querySelector('input');
    expect(input).not.toBeNull();  // FAILS 

    const bar = el.querySelector('ion-searchbar');
    expect(bar.innerHTML).not.toEqual(''); // FAILS
    expect(bar.shadowRoot).not.toBeNull();  // FAILS

HTML Page

<ion-header>
  <ion-toolbar>
    <ion-title>
      Test Page
    </ion-title>
  </ion-toolbar>
</ion-header>

<ion-content padding>
  <ion-searchbar></ion-searchbar>
</ion-content>

Component Class

import { Component } from '@angular/core';

@Component({
  selector: 'app-test',
  templateUrl: './test.page.html',
  styleUrls: ['./test.page.scss'],
})
export class TestPage {

  constructor() { }

}

Test Spec

import { CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
import { async, ComponentFixture, TestBed } from '@angular/core/testing';

import { TestPage } from './test.page';

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

beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ TestPage ],
      schemas: [CUSTOM_ELEMENTS_SCHEMA],
    })
    .compileComponents();

  }));

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

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

  it('should have an searchbar', () => {
    const el: HTMLElement = fixture.nativeElement;
    const bar = el.querySelector('ion-searchbar');
    fixture.detectChanges();
    expect(bar).not.toBeNull();  // FAILS
    expect(bar.shadowRoot).not.toBeNull();  // FAILS
  });

  it('should have an input field', () => {
    const el: HTMLElement = fixture.nativeElement;
    const input = el.querySelector('input');
    expect(input).not.toBeNull();  // FAILS
  });

});