feat(gateway): gRPC server ReadTag (C4)

tests/unit/adapters/test_grpc_server.py

@@ -0,0 +1,96 @@
+from unittest.mock import AsyncMock, MagicMock
+
+import grpc
+import pytest
+
+from ingestor.adapters.grpc_server import GrpcServer, ReadTagServicer
+from ingestor.proto.opc_gateway_pb2 import ReadTagRequest
+
+
+def make_request(server_id='srv1', addr='ns=2;i=5'):
+    return ReadTagRequest(server_id=server_id, addr=addr, data_type='float')
+
+
+@pytest.mark.asyncio
+async def test_read_tag_maps_full_result_onto_response():
+    active_read = AsyncMock()
+    active_read.read_now.return_value = {
+        'value': 1.5,
+        'opc_status_code': 'Good',
+        'source_timestamp': '2026-07-15T10:00:00-03:00',
+        'server_timestamp': '2026-07-15T10:00:01-03:00',
+        'persisted': False,
+    }
+    servicer = ReadTagServicer(active_read, MagicMock())
+
+    response = await servicer.ReadTag(make_request(), AsyncMock())
+
+    assert response.value == '1.5'
+    assert response.opc_status_code == 'Good'
+    assert response.source_timestamp == '2026-07-15T10:00:00-03:00'
+    assert response.server_timestamp == '2026-07-15T10:00:01-03:00'
+    assert response.persisted is False
+
+
+@pytest.mark.asyncio
+async def test_read_tag_none_timestamps_become_empty_string():
+    active_read = AsyncMock()
+    active_read.read_now.return_value = {
+        'value': 1.5,
+        'opc_status_code': None,
+        'source_timestamp': None,
+        'server_timestamp': None,
+        'persisted': False,
+    }
+    servicer = ReadTagServicer(active_read, MagicMock())
+
+    response = await servicer.ReadTag(make_request(), AsyncMock())
+
+    assert response.opc_status_code == ''
+    assert response.source_timestamp == ''
+    assert response.server_timestamp == ''
+
+
+@pytest.mark.asyncio
+async def test_read_tag_aborts_with_internal_on_engine_failure():
+    active_read = AsyncMock()
+    active_read.read_now.side_effect = RuntimeError('boom')
+    logger = MagicMock()
+    servicer = ReadTagServicer(active_read, logger)
+    context = AsyncMock()
+    context.abort.side_effect = grpc.RpcError('aborted')
+
+    with pytest.raises(grpc.RpcError):
+        await servicer.ReadTag(make_request(), context)
+
+    context.abort.assert_awaited_once()
+    args = context.abort.call_args.args
+    assert args[0] == grpc.StatusCode.INTERNAL
+    logger.error.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_read_tag_uses_slot_lookup_names_when_provided():
+    active_read = AsyncMock()
+    active_read.read_now.return_value = {
+        'value': 1,
+        'opc_status_code': 'Good',
+        'source_timestamp': None,
+        'server_timestamp': None,
+        'persisted': True,
+    }
+    names = [{'collection': 'c1', 'name': 't1'}]
+    slot_lookup = MagicMock(return_value=names)
+    servicer = ReadTagServicer(active_read, MagicMock(), slot_lookup=slot_lookup)
+
+    await servicer.ReadTag(make_request(server_id='srv1', addr='ns=2;i=5'), AsyncMock())
+
+    slot_lookup.assert_called_once_with('srv1', 'ns=2;i=5')
+    active_read.read_now.assert_awaited_once_with('srv1', 'ns=2;i=5', names=names)
+
+
+@pytest.mark.asyncio
+async def test_grpc_server_stop_before_start_does_not_raise():
+    server = GrpcServer(active_read=AsyncMock(), logger=MagicMock())
+
+    await server.stop()  # no raise