Move part of image_processing tests (#5634)

* Move part of image_processing tests

* fix lint

tests/testing_config/custom_components/image_processing/test.py

@@ -0,0 +1,49 @@
+"""Provide a mock image processing."""
+
+from homeassistant.components.image_processing import ImageProcessingEntity
+
+
+def setup_platform(hass, config, add_devices, discovery_info=None):
+    """Setup the test image_processing platform."""
+    add_devices([TestImageProcessing('camera.demo_camera', "Test")])
+
+
+class TestImageProcessing(ImageProcessingEntity):
+    """Test image processing entity."""
+
+    def __init__(self, camera_entity, name):
+        """Initialize test image processing."""
+        self._name = name
+        self._camera = camera_entity
+        self._count = 0
+        self._image = ""
+
+    @property
+    def should_poll(self):
+        """Return True if entity has to be polled for state."""
+        return False
+
+    @property
+    def camera_entity(self):
+        """Return camera entity id from process pictures."""
+        return self._camera
+
+    @property
+    def name(self):
+        """Return the name of the entity."""
+        return self._name
+
+    @property
+    def state(self):
+        """Return the state of the entity."""
+        return self._count
+
+    @property
+    def device_state_attributes(self):
+        """Return device specific state attributes."""
+        return {'image': self._image}
+
+    def process_image(self, image):
+        """Process image."""
+        self._image = image
+        self._count += 1