Simple selector function useful in testing environments. Throws error to indicate that the test has failed

queryElement.ts

/**
 * Locates a descendant of `rootElement` given selector provided
 * or throws error if output element is not found 
 * or is not an instance of input `DomElementClass`.
 * 
 * ### Example
 * 
 * ```ts
 * const btn = queryElement(
 *   renderRes.container,
 *   'button[type="submit"]',
 *   HTMLButtonElement
 * );
 * ```
 * 
 * @param rootElement 
 * @param selector 
 * @param DomElementClass 
 * @returns 
 */
function queryElement<Elem extends Element>(
  rootElement: Element,
  selector: string,
  DomElementClass: new () => Elem
): Elem {
  const output = rootElement.querySelector(selector);

  if (!(output instanceof DomElementClass)) {
    throw new Error(
      `queryElement ${selector} not found in root ${rootElement.tagName}`
    );
  }

  return output;
}