Add validation of content_type to image entity (#95248)

tests/components/image/conftest.py

@@ -36,6 +36,21 @@ class MockImageEntity(image.ImageEntity):
         return b"Test"
 
 
+class MockImageEntityInvalidContentType(image.ImageEntity):
+    """Mock image entity."""
+
+    _attr_name = "Test"
+
+    async def async_added_to_hass(self):
+        """Set the update time and assign and incorrect content type."""
+        self._attr_content_type = "text/json"
+        self._attr_image_last_updated = dt_util.utcnow()
+
+    async def async_image(self) -> bytes | None:
+        """Return bytes of image."""
+        return b"Test"
+
+
 class MockURLImageEntity(image.ImageEntity):
     """Mock image entity."""
 
@@ -125,7 +140,9 @@ def config_flow_fixture(hass: HomeAssistant) -> Generator[None, None, None]:
 
 
 @pytest.fixture(name="mock_image_config_entry")
-async def mock_image_config_entry_fixture(hass: HomeAssistant, config_flow: None):
+async def mock_image_config_entry_fixture(
+    hass: HomeAssistant, config_flow: None
+) -> ConfigEntry:
     """Initialize a mock image config_entry."""
 
     async def async_setup_entry_init(
@@ -166,7 +183,7 @@ async def mock_image_config_entry_fixture(hass: HomeAssistant, config_flow: None
 
 
 @pytest.fixture(name="mock_image_platform")
-async def mock_image_platform_fixture(hass: HomeAssistant):
+async def mock_image_platform_fixture(hass: HomeAssistant) -> None:
     """Initialize a mock image platform."""
     mock_integration(hass, MockModule(domain="test"))
     mock_platform(hass, "test.image", MockImagePlatform([MockImageEntity(hass)]))