Add test

javascript/src/ycell.ts

@@ -753,6 +753,9 @@ export class YCodeCell
   set outputs(v: Array<nbformat.IOutput>) {
     this.setOutputs(v);
   }
+  get youtputs(): Y.Array<any> {
+    return this._youtputs;
+  }
 
   /**
    * Execution, display, or stream outputs.

tests/files/nb1.ipynb

@@ -0,0 +1,43 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "id": "4166c837-41c7-4ada-b86e-fd9a7720a409",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Hello,"
+     ]
+    }
+   ],
+   "source": [
+    "print(\"Hello,\", end=\"\")"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.12.3"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

tests/test_pycrdt_yjs.py

@@ -74,6 +74,31 @@ async def test_ypy_yjs_0(yws_server, yjs_client):
         assert ytest.source == nb
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize("yjs_client", "1", indirect=True)
+async def test_ypy_yjs_1(yws_server, yjs_client):
+    ydoc = Doc()
+    ynotebook = YNotebook(ydoc)
+    async with connect("ws://localhost:1234/my-roomname") as websocket, WebsocketProvider(
+        ydoc, websocket
+    ):
+        nb = stringify_source(json.loads((files_dir / "nb1.ipynb").read_text()))
+        ynotebook.source = nb
+        output_text = ynotebook.ycells[0]["outputs"][0]["text"]
+        assert output_text.to_py() == ["Hello,"]
+        event = Event()
+
+        def callback(_event):
+            event.set()
+
+        output_text.observe(callback)
+
+        with move_on_after(10):
+            await event.wait()
+
+        assert output_text.to_py() == ["Hello,", " World!"]
+
+
 def test_plotly_renderer():
     """This test checks in particular that the type cast is not breaking the data."""
     ydoc = Doc()

tests/yjs_client_1.js

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) Jupyter Development Team.
+ * Distributed under the terms of the Modified BSD License.
+ */
+
+import { YNotebook } from '@jupyter/ydoc'
+import { WebsocketProvider } from 'y-websocket'
+import ws from 'ws'
+
+const notebook = new YNotebook()
+const cells = notebook.ydoc.getArray('cells')
+
+function append_text() {
+  const cell = notebook.getCell(0)
+  const youtput = cell.youtputs.get(0)
+  const text = youtput.get('text')
+  text.insert(1, [' World!'])
+}
+
+function callback2(event) {
+  if (event.transaction.local) {
+    return
+  }
+
+  const cell = notebook.getCell(0)
+  if (cell.youtputs.length > 0) {
+    setTimeout(append_text, 100)
+  }
+}
+
+function callback1(event) {
+  if (event.transaction.local) {
+    return
+  }
+
+  if (cells.length > 0) {
+    const cell = notebook.getCell(0)
+    if (cell.youtputs.length > 0) {
+      setTimeout(append_text, 100)
+    }
+    else {
+      cell.youtputs.observe(callback2)
+    }
+  }
+}
+
+cells.observe(callback1)
+
+const wsProvider = new WebsocketProvider(
+  'ws://localhost:1234', 'my-roomname',
+  notebook.ydoc,
+  { WebSocketPolyfill: ws }
+)