MVP implementation of Backup sync agents

tests/components/backup/snapshots/test_websocket.ambr

@@ -1,23 +1,19 @@
 # serializer version: 1
 # name: test_agents_download[with_hassio]
-  _Call(
-    tuple(
-    ),
-    dict({
-      'id': 'abc123',
-      'path': PosixPath('/workspaces/core/tests/testing_config/backup/abc123.tar'),
-    }),
-  )
+  dict({
+    'id': 1,
+    'result': None,
+    'success': True,
+    'type': 'result',
+  })
 # ---
 # name: test_agents_download[without_hassio]
-  _Call(
-    tuple(
-    ),
-    dict({
-      'id': 'abc123',
-      'path': PosixPath('/workspaces/core/tests/testing_config/backup/abc123.tar'),
-    }),
-  )
+  dict({
+    'id': 1,
+    'result': None,
+    'success': True,
+    'type': 'result',
+  })
 # ---
 # name: test_agents_download_exception
   dict({

tests/components/backup/test_websocket.py

@@ -1,5 +1,6 @@
 """Tests for the Backup integration."""
 
+from pathlib import Path
 from unittest.mock import AsyncMock, patch
 
 import pytest
@@ -313,8 +314,11 @@ async def test_agents_download(
         }
     )
     with patch.object(BackupSyncAgentTest, "async_download_backup") as download_mock:
-        assert await client.receive_json()
-        assert snapshot == download_mock.call_args
+        assert snapshot == await client.receive_json()
+        assert download_mock.call_args[1] == {
+            "id": "abc123",
+            "path": Path(hass.config.path("backup"), "abc123.tar"),
+        }
 
 
 async def test_agents_download_exception(