WRNexusJS/packages/react/test/island-hmr.test.ts

import { afterEach, expect, test } from "bun:test";
import { Window } from "happy-dom";
import { act, createElement } from "react";
import { islandRootCount, mountIslands, remountIslands, unmountIslands } from "../src/island-runtime.ts";

(globalThis as any).IS_REACT_ACT_ENVIRONMENT = true;

function host(window: Window): ParentNode {
  return window.document.body as unknown as ParentNode;
}

function domWith(html: string) {
  const window = new Window();
  window.document.body.innerHTML = html;
  (globalThis as any).window = window;
  (globalThis as any).document = window.document;
  return window;
}

afterEach(() => {
  const doc = (globalThis as any).document;
  if (!doc) return;
  act(() => {
    unmountIslands(doc);
  });
});

const marker =
  `<div data-wrn-island="Chart" data-wrn-island-strategy="only"` +
  ` data-wrn-island-props='{}'></div>`;

test("remount replaces island output without leaking roots", async () => {
  const window = domWith(marker);

  const first = async () => ({ default: () => createElement("span", null, "v1") });
  const second = async () => ({ default: () => createElement("span", null, "v2") });

  await act(async () => {
    await mountIslands(host(window), { loader: first });
  });
  expect(window.document.body.textContent).toContain("v1");
  expect(islandRootCount()).toBe(1);

  await act(async () => {
    await remountIslands(host(window), { loader: second });
  });
  expect(window.document.body.textContent).toContain("v2");
  expect(window.document.body.textContent).not.toContain("v1");
  expect(islandRootCount()).toBe(1);
});

test("repeated remounts stay at one root", async () => {
  const window = domWith(marker);
  const loader = async () => ({ default: () => createElement("span", null, "x") });

  await act(async () => {
    await mountIslands(host(window), { loader });
  });

  for (let i = 0; i < 4; i += 1) {
    await act(async () => {
      await remountIslands(host(window), { loader });
    });
  }

  expect(islandRootCount()).toBe(1);
});