web/test/test-util.ts

/**
 * @license
 * Copyright (C) 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
export function queryAll<E extends Element = Element>(
  el: Element,
  selector: string
): NodeListOf<E> {
  if (!el) throw new Error('element not defined');
  const root = el.shadowRoot ?? el;
  return root.querySelectorAll<E>(selector);
}

export function query<E extends Element = Element>(
  el: Element | undefined,
  selector: string
): E | undefined {
  if (!el) return undefined;
  const root = el.shadowRoot ?? el;
  return root.querySelector<E>(selector) ?? undefined;
}

export function queryAndAssert<E extends Element = Element>(
  el: Element | undefined,
  selector: string
): E {
  const found = query<E>(el, selector);
  if (!found) throw new Error(`selector '${selector}' did not match anything'`);
  return found;
}