Remove mDNS iteration from Plugwise unique ID (#78680)

* Remove mDNS iteration from Plugwise unique ID

* Add iteration to tests

homeassistant/components/plugwise/config_flow.py

@@ -91,7 +91,7 @@ class PlugwiseConfigFlow(ConfigFlow, domain=DOMAIN):
         self.discovery_info = discovery_info
         _properties = discovery_info.properties
 
-        unique_id = discovery_info.hostname.split(".")[0]
+        unique_id = discovery_info.hostname.split(".")[0].split("-")[0]
         if config_entry := await self.async_set_unique_id(unique_id):
             try:
                 await validate_gw_input(

tests/components/plugwise/test_config_flow.py

@@ -36,7 +36,8 @@ TEST_USERNAME2 = "stretch"
 TEST_DISCOVERY = ZeroconfServiceInfo(
     host=TEST_HOST,
     addresses=[TEST_HOST],
-    hostname=f"{TEST_HOSTNAME}.local.",
+    # The added `-2` is to simulate mDNS collision
+    hostname=f"{TEST_HOSTNAME}-2.local.",
     name="mock_name",
     port=DEFAULT_PORT,
     properties={