Auto-increment port number in microgrid client tests

This is a hack to avoid the inherent flakiness of the approach of using
a real GRPC (mock) server. The server seems to stay alive for a short
time after the test is finished, which causes the next test to fail
because the port is already in use.

This is a workaround until we have can get rid of the real GRPC server.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

tests/microgrid/test_client.py

@@ -35,11 +35,22 @@
 # pylint: disable=missing-class-docstring,no-member
 
 
+# This incrementing port is a hack to avoid the inherent flakiness of the approach of
+# using a real GRPC (mock) server. The server seems to stay alive for a short time after
+# the test is finished, which causes the next test to fail because the port is already
+# in use.
+# This is a workaround until we have a better solution.
+# See https://github.com/frequenz-floss/frequenz-sdk-python/issues/662
+_CURRENT_PORT: int = 57897
+
+
 @contextlib.asynccontextmanager
 async def _gprc_server(
-    port: int,
     servicer: mock_api.MockMicrogridServicer | None = None,
 ) -> AsyncIterator[tuple[mock_api.MockMicrogridServicer, client.MicrogridApiClient]]:
+    global _CURRENT_PORT  # pylint: disable=global-statement
+    port = _CURRENT_PORT
+    _CURRENT_PORT += 1
     if servicer is None:
         servicer = mock_api.MockMicrogridServicer()
     server = mock_api.MockGrpcServer(servicer, port=port)
@@ -60,7 +71,7 @@ class TestMicrogridGrpcClient:
 
     async def test_components(self) -> None:
         """Test the components() method."""
-        async with _gprc_server(57899) as (servicer, microgrid):
+        async with _gprc_server() as (servicer, microgrid):
             assert set(await microgrid.components()) == set()
 
             servicer.add_component(
@@ -174,7 +185,7 @@ async def test_components(self) -> None:
 
     async def test_connections(self) -> None:
         """Test the connections() method."""
-        async with _gprc_server(57898) as (servicer, microgrid):
+        async with _gprc_server() as (servicer, microgrid):
             assert set(await microgrid.connections()) == set()
 
             servicer.add_connection(0, 0)
@@ -336,7 +347,7 @@ def ListAllComponents(
             ) -> microgrid_pb.ComponentList:
                 return microgrid_pb.ComponentList(components=self._components)
 
-        async with _gprc_server(57897, BadServicer()) as (servicer, microgrid):
+        async with _gprc_server(BadServicer()) as (servicer, microgrid):
             assert list(await microgrid.connections()) == []
             for component_id in [1, 2, 3, 4, 5, 6, 7, 8, 9]:
                 servicer.add_component(
@@ -382,7 +393,7 @@ def ListAllComponents(
 
     async def test_meter_data(self) -> None:
         """Test the meter_data() method."""
-        async with _gprc_server(57899) as (servicer, microgrid):
+        async with _gprc_server() as (servicer, microgrid):
             servicer.add_component(
                 83, components_pb.ComponentCategory.COMPONENT_CATEGORY_METER
             )
@@ -406,7 +417,7 @@ async def test_meter_data(self) -> None:
 
     async def test_battery_data(self) -> None:
         """Test the battery_data() method."""
-        async with _gprc_server(57899) as (servicer, microgrid):
+        async with _gprc_server() as (servicer, microgrid):
             servicer.add_component(
                 83, components_pb.ComponentCategory.COMPONENT_CATEGORY_BATTERY
             )
@@ -430,7 +441,7 @@ async def test_battery_data(self) -> None:
 
     async def test_inverter_data(self) -> None:
         """Test the inverter_data() method."""
-        async with _gprc_server(57899) as (servicer, microgrid):
+        async with _gprc_server() as (servicer, microgrid):
             servicer.add_component(
                 83, components_pb.ComponentCategory.COMPONENT_CATEGORY_INVERTER
             )
@@ -454,7 +465,7 @@ async def test_inverter_data(self) -> None:
 
     async def test_ev_charger_data(self) -> None:
         """Test the ev_charger_data() method."""
-        async with _gprc_server(57899) as (servicer, microgrid):
+        async with _gprc_server() as (servicer, microgrid):
             servicer.add_component(
                 83, components_pb.ComponentCategory.COMPONENT_CATEGORY_EV_CHARGER
             )
@@ -478,7 +489,7 @@ async def test_ev_charger_data(self) -> None:
 
     async def test_charge(self) -> None:
         """Check if charge is able to charge component."""
-        async with _gprc_server(57899) as (servicer, microgrid):
+        async with _gprc_server() as (servicer, microgrid):
             servicer.add_component(
                 83, components_pb.ComponentCategory.COMPONENT_CATEGORY_METER
             )
@@ -491,7 +502,7 @@ async def test_charge(self) -> None:
 
     async def test_discharge(self) -> None:
         """Check if discharge is able to discharge component."""
-        async with _gprc_server(57899) as (servicer, microgrid):
+        async with _gprc_server() as (servicer, microgrid):
             servicer.add_component(
                 73, components_pb.ComponentCategory.COMPONENT_CATEGORY_METER
             )
@@ -504,7 +515,7 @@ async def test_discharge(self) -> None:
 
     async def test_set_bounds(self) -> None:
         """Check if set_bounds is able to set bounds for component."""
-        async with _gprc_server(57899) as (servicer, microgrid):
+        async with _gprc_server() as (servicer, microgrid):
             servicer.add_component(
                 38, components_pb.ComponentCategory.COMPONENT_CATEGORY_INVERTER
             )