Mocking Custom Element Lifecycle Registrations via Proxy Objects for React DOM Interop Tests

import React from 'react';
 
export function createCustomElementRegistryProxy(onRegister) {
  const targetRegistry = window.customElements;
  if (!targetRegistry) {
    throw new Error('CustomElementRegistry is missing from window environment.');
  }
 
  return new Proxy(targetRegistry, {
    get(target, prop, receiver) {
      if (prop === 'define') {
        return function (tagName, constructorClass, options) {
          if (!(constructorClass.prototype instanceof HTMLElement)) {
            throw new TypeError('Custom element constructor must extend HTMLElement.');
          }
          if (typeof onRegister === 'function') {
            onRegister(tagName, constructorClass);
          }
          return Reflect.apply(target.define, target, [tagName, constructorClass, options]);
        };
      }
      const value = Reflect.get(target, prop, receiver);
      return typeof value === 'function' ? value.bind(target) : value;
    }
  });
}