Add a reproduction of the issue reported in #488

This test is not in the right place, but I'm not sure where the
problem is yet.

Author: msakrejda

packages/automerge-repo-react-hooks/test/useRepo.test.tsx

@@ -1,8 +1,9 @@
 import { Repo } from "@automerge/automerge-repo"
-import { render } from "@testing-library/react"
+import { render, waitFor } from "@testing-library/react"
 import React from "react"
 import { describe, expect, test, vi } from "vitest"
 import { RepoContext, useRepo } from "../src/useRepo.js"
+import { setupPairedRepos } from "./testSetup.js"
 
 describe("useRepo", () => {
   const Component = ({ onRepo }: { onRepo: (repo: Repo) => void }) => {
@@ -30,4 +31,17 @@ describe("useRepo", () => {
     render(<Component onRepo={onRepo} />, { wrapper })
     expect(onRepo).toHaveBeenLastCalledWith(repo)
   })
+
+  test("should synchronize empty documents", async () => {
+    const { repoCreator, repoFinder } = setupPairedRepos();
+
+    const handle = repoCreator.create({});
+
+    await waitFor(async () => {
+      repoFinder.find(handle.documentId);
+    })
+
+    const finderHandle = await repoFinder.find(handle.documentId);
+    expect(finderHandle.doc).toEqual(handle.doc);
+  })
 })