[mqtt] Fix crash with empty broker during upload/logs (#11866)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

tests/unit_tests/test_mqtt.py

@@ -0,0 +1,91 @@
+"""Unit tests for esphome.mqtt module."""
+
+from __future__ import annotations
+
+import pytest
+
+from esphome.const import CONF_BROKER, CONF_ESPHOME, CONF_MQTT, CONF_NAME
+from esphome.core import EsphomeError
+from esphome.mqtt import get_esphome_device_ip
+
+
+def test_get_esphome_device_ip_empty_broker() -> None:
+    """Test that get_esphome_device_ip raises EsphomeError when broker is empty."""
+    config = {
+        CONF_MQTT: {
+            CONF_BROKER: "",
+        },
+        CONF_ESPHOME: {
+            CONF_NAME: "test-device",
+        },
+    }
+
+    with pytest.raises(
+        EsphomeError,
+        match="Cannot discover IP via MQTT as the broker is not configured",
+    ):
+        get_esphome_device_ip(config)
+
+
+def test_get_esphome_device_ip_none_broker() -> None:
+    """Test that get_esphome_device_ip raises EsphomeError when broker is None."""
+    config = {
+        CONF_MQTT: {
+            CONF_BROKER: None,
+        },
+        CONF_ESPHOME: {
+            CONF_NAME: "test-device",
+        },
+    }
+
+    with pytest.raises(
+        EsphomeError,
+        match="Cannot discover IP via MQTT as the broker is not configured",
+    ):
+        get_esphome_device_ip(config)
+
+
+def test_get_esphome_device_ip_missing_mqtt() -> None:
+    """Test that get_esphome_device_ip raises EsphomeError when mqtt config is missing."""
+    config = {
+        CONF_ESPHOME: {
+            CONF_NAME: "test-device",
+        },
+    }
+
+    with pytest.raises(
+        EsphomeError,
+        match="Cannot discover IP via MQTT as the config does not include the mqtt:",
+    ):
+        get_esphome_device_ip(config)
+
+
+def test_get_esphome_device_ip_missing_esphome() -> None:
+    """Test that get_esphome_device_ip raises EsphomeError when esphome config is missing."""
+    config = {
+        CONF_MQTT: {
+            CONF_BROKER: "mqtt.local",
+        },
+    }
+
+    with pytest.raises(
+        EsphomeError,
+        match="Cannot discover IP via MQTT as the config does not include the device name:",
+    ):
+        get_esphome_device_ip(config)
+
+
+def test_get_esphome_device_ip_missing_name() -> None:
+    """Test that get_esphome_device_ip raises EsphomeError when device name is missing."""
+    config = {
+        CONF_MQTT: {
+            CONF_BROKER: "mqtt.local",
+        },
+        CONF_ESPHOME: {},
+    }
+
+    with pytest.raises(
+        EsphomeError,
+        match="Cannot discover IP via MQTT as the config does not include the device name:",
+    ):
+        get_esphome_device_ip(config)