Add test for empty image properties annotation.

vision/unit_tests/test_color.py

@@ -40,7 +40,7 @@ def test_rgb_color_data(self):
         self.assertEqual(colors.blue, 255.0)
         self.assertEqual(colors.alpha, 0.5)
 
-    def test_pb_no_rgb_color_data(self):
+    def test_empty_pb_rgb_color_data(self):
         from google.type.color_pb2 import Color
 
         color_pb = Color()
@@ -94,7 +94,7 @@ def _get_target_class():
         from google.cloud.vision.color import ImagePropertiesAnnotation
         return ImagePropertiesAnnotation
 
-    def test_color_annotation_from_pb(self):
+    def test_image_properties_annotation_from_pb(self):
         from google.cloud.grpc.vision.v1 import image_annotator_pb2
         from google.protobuf.wrappers_pb2 import FloatValue
         from google.type.color_pb2 import Color
@@ -119,3 +119,12 @@ def test_color_annotation_from_pb(self):
         self.assertEqual(image_properties.colors[0].color.green, 2.0)
         self.assertEqual(image_properties.colors[0].color.blue, 3.0)
         self.assertEqual(image_properties.colors[0].color.alpha, 1.0)
+
+    def test_empty_image_properties_annotation_from_pb(self):
+        from google.cloud.grpc.vision.v1 import image_annotator_pb2
+
+        image_properties_pb = image_annotator_pb2.ImageProperties()
+
+        color_info = self._get_target_class()
+        image_properties = color_info.from_pb(image_properties_pb)
+        self.assertIsNone(image_properties)