* (Re)send the configuration payload once it changes (e.g. due to

  interpolation). The entities are tracked using hash of JSON formatted
  configuration payloads sent, and compared for any change to make a decision
  it should be sent again
+ `EnergomeraConfig`: introduced `_read_config` method dedicated to reading
  configuration file, for ease of mocks during testing
* Better test organization by moving fixtures `mock_serial`, `mock_mqtt`,
  `mock_config` to `conftest.py` and making those configurable via `pytest`
  markers
* `EnergomeraConfig` class no longer requires mocking `patch` built-in,
  since the class now has `_read_config()` method easily mocked
* `test_energomera` no longer generates separate tests for each
   particular MQTT and serial call - those are now validates by single test as
   the whole flow
+ Added tests for handling HomeAssistant configuration payloads, especialy for
  resending those once the payload changes

pyproject.toml

@@ -15,6 +15,9 @@ log_cli_level = "error"
 
 markers = [
     "mqtt_broker_users",
+    "serial_simulate_timeout",
+    "serial_exchange",
+    "config_yaml"
 ]
 
 [tool.pylint.main]

src/energomera_hass_mqtt/__init__.py

@@ -54,9 +54,9 @@ class IecToHassSensor:  # pylint: disable=too-many-instance-attributes
 
     # Class attribute to store HASS sensors having config payload sent, to
     # ensure it is done only once per multiple instantiations of the class -
-    # HASS needs sensor disocvery only once, otherwise logs a message re:
+    # HASS needs sensor discovery only once, otherwise logs a message re:
     # sensor has already been discovered
-    _hass_config_entities_published = {}
+    hass_config_payloads_published = {}
     # Class attribute defining MQTT topic base for HASS discovery
     _mqtt_topic_base = 'sensor'
 
@@ -259,15 +259,17 @@ async def process(self, setup_only=False):
                 if setup_only:
                     continue
 
-                # Send payloads using MQTT
-                # Send config payload for HomeAssistant discovery only once
-                # per sensor
-                if (self._hass_unique_id not in
-                        self._hass_config_entities_published):
-
-                    # Config payload for sensor discovery
-                    config_payload = self.hass_config_payload()
-                    json_config_payload = json.dumps(config_payload)
+                # Send configuration payloads using MQTT once per sensor
+                config_payload = self.hass_config_payload()
+                json_config_payload = json.dumps(config_payload)
+                config_payload_sent_hash = (
+                    self.hass_config_payloads_published.get(
+                        self._hass_unique_id, None
+                    )
+                )
+                # (re)send the configuration payload once it changes (e.g. due
+                # to interpolation)
+                if config_payload_sent_hash != hash(json_config_payload):
                     _LOGGER.debug("MQTT config payload for HASS"
                                   " auto-discovery: '%s'",
                                   json_config_payload)
@@ -277,10 +279,10 @@ async def process(self, setup_only=False):
                         payload=json_config_payload,
                         retain=True,
                     )
-                    # Mark the config payload for the given sensor as sent
-                    self._hass_config_entities_published[
+                    # Keep track of JSON formatted configuration payloads sent
+                    self.hass_config_payloads_published[
                         self._hass_unique_id
-                    ] = True
+                    ] = hash(json_config_payload)
 
                     _LOGGER.debug("Sent HASS config payload to MQTT topic"
                                   " '%s'",
@@ -459,6 +461,11 @@ def __init__(
         self._serial_number = None
         self._sw_version = None
 
+        # (re)initialize what configuration payloads have been sent across all
+        # instances of `IecToHassSensor`. Mostly used by tests, as
+        # `async_main()` instantiates the class only once
+        IecToHassSensor.hass_config_payloads_published = {}
+
     def iec_read_values(self, address, additional_data=None):
         """
         Reads value(s) at selected address from the meter using IEC 62056-21

src/energomera_hass_mqtt/config.py

@@ -188,6 +188,19 @@ def _get_schema(self):
             ],
         })
 
+    @staticmethod
+    def _read_config(config_file):
+        """
+        Reads configuration file.
+
+        :param str config_file: Name of configuration file
+        :return str: Configuration file contents
+        """
+        with open(config_file, encoding='ascii') as file:
+            content = file.read()
+
+        return content
+
     def __init__(self, config_file=None, content=None):
         """
         Initializes configuration state either from file or content string.
@@ -202,8 +215,7 @@ def __init__(self, config_file=None, content=None):
 
         try:
             if not content:
-                with open(config_file, encoding='ascii') as file:
-                    content = file.read()
+                content = self._read_config(config_file)
 
             config = yaml.safe_load(content)
         except (yaml.YAMLError, OSError) as exc: