Extract HTML5 SSE helpers

services/api-server/tests/test_api.py

@@ -7,6 +7,7 @@ import zipfile
 from fastapi.testclient import TestClient
 
 from api_server import main
+from api_server.html5_sse import html5_sse_comment, html5_sse_event, html5_sse_if_changed
 from api_server.main import app
 from one_c_normalizer import ConfigurationRoot, MetadataGroup, MetadataObject, Module, NormalizedProject
 
@@ -51,6 +52,26 @@ def assert_html5_response_contract(response, *markers: str, full_page: bool = Fa
     assert_html5_contract(response.text, *markers, full_page=full_page)
 
 
+def test_html5_sse_formatters_emit_stable_event_stream_chunks():
+    assert html5_sse_comment("heartbeat") == ": heartbeat\n\n"
+    assert html5_sse_event("status", "<div>\nready</div>") == (
+        "event: status\n"
+        "retry: 5000\n"
+        "data: <div>\n"
+        "data: ready</div>\n\n"
+    )
+
+    last_fragments: dict[str, str] = {}
+    first = list(html5_sse_if_changed(last_fragments, "status", "<div>ready</div>"))
+    second = list(html5_sse_if_changed(last_fragments, "status", "<div>ready</div>"))
+    third = list(html5_sse_if_changed(last_fragments, "status", "<div>done</div>"))
+
+    assert len(first) == 1
+    assert second == []
+    assert len(third) == 1
+    assert "data: <div>done</div>" in third[0]
+
+
 def test_cors_allows_lan_panel_origin():
     client = TestClient(app)
     response = client.options(