Add a unit test for the tag_proto_objects method (#2163)

* Add a unit test for the tag_proto_objects method

Signed-off-by: Achal Shah <achals@gmail.com>

* fix tests

Signed-off-by: Achal Shah <achals@gmail.com>

sdk/python/tests/unit/diff/test_fco_diff.py

@@ -0,0 +1,75 @@
+from feast.diff.FcoDiff import diff_between, tag_proto_objects_for_keep_delete_add
+from feast.feature_view import FeatureView
+from tests.utils.data_source_utils import prep_file_source
+
+
+def test_tag_proto_objects_for_keep_delete_add(simple_dataset_1):
+    with prep_file_source(
+        df=simple_dataset_1, event_timestamp_column="ts_1"
+    ) as file_source:
+        to_delete = FeatureView(
+            name="to_delete", entities=["id"], batch_source=file_source, ttl=None,
+        ).to_proto()
+        unchanged_fv = FeatureView(
+            name="fv1", entities=["id"], batch_source=file_source, ttl=None,
+        ).to_proto()
+        pre_changed = FeatureView(
+            name="fv2",
+            entities=["id"],
+            batch_source=file_source,
+            ttl=None,
+            tags={"when": "before"},
+        ).to_proto()
+        post_changed = FeatureView(
+            name="fv2",
+            entities=["id"],
+            batch_source=file_source,
+            ttl=None,
+            tags={"when": "after"},
+        ).to_proto()
+        to_add = FeatureView(
+            name="to_add", entities=["id"], batch_source=file_source, ttl=None,
+        ).to_proto()
+
+        keep, delete, add = tag_proto_objects_for_keep_delete_add(
+            [unchanged_fv, pre_changed, to_delete], [unchanged_fv, post_changed, to_add]
+        )
+
+        assert len(list(keep)) == 2
+        assert unchanged_fv in keep
+        assert post_changed in keep
+        assert pre_changed not in keep
+        assert len(list(delete)) == 1
+        assert to_delete in delete
+        assert len(list(add)) == 1
+        assert to_add in add
+
+
+def test_diff_between_feature_views(simple_dataset_1):
+    with prep_file_source(
+        df=simple_dataset_1, event_timestamp_column="ts_1"
+    ) as file_source:
+        pre_changed = FeatureView(
+            name="fv2",
+            entities=["id"],
+            batch_source=file_source,
+            ttl=None,
+            tags={"when": "before"},
+        ).to_proto()
+        post_changed = FeatureView(
+            name="fv2",
+            entities=["id"],
+            batch_source=file_source,
+            ttl=None,
+            tags={"when": "after"},
+        ).to_proto()
+
+        fco_diffs = diff_between(pre_changed, pre_changed, "feature view")
+        assert len(fco_diffs.fco_property_diffs) == 0
+
+        fco_diffs = diff_between(pre_changed, post_changed, "feature view")
+        assert len(fco_diffs.fco_property_diffs) == 1
+
+        assert fco_diffs.fco_property_diffs[0].property_name == "tags"
+        assert fco_diffs.fco_property_diffs[0].val_existing == {"when": "before"}
+        assert fco_diffs.fco_property_diffs[0].val_declared == {"when": "after"}