unit test for pickling (flyteorg#2805)

tests/flytekit/unit/core/test_type_hints.py

@@ -29,6 +29,7 @@
 from flytekit.core.node import Node
 from flytekit.core.promise import NodeOutput, Promise, VoidPromise
 from flytekit.core.resources import Resources
+from flytekit.types.pickle.pickle import FlytePickleTransformer
 from flytekit.core.task import TaskMetadata, task
 from flytekit.core.testing import patch, task_mock
 from flytekit.core.type_engine import RestrictedTypeError, SimpleTransformer, TypeEngine, TypeTransformerFailedError
@@ -115,6 +116,37 @@ def my_task(a: int):
     assert context_manager.FlyteContextManager.size() == 1
 
 
+def test_transformer_override():
+    tf = FlytePickleTransformer()
+
+    @task
+    def my_task() -> Annotated[str, tf]:
+        return "Hello world"
+
+    @workflow
+    def wf() -> FlyteFile:
+        return my_task()
+
+    annotated_output = wf()
+
+    @task
+    def my_task_any() -> typing.Any:
+        return "Hello world"
+
+    @workflow
+    def wf_any() -> FlyteFile:
+        return my_task_any()
+
+    any_output = wf_any()
+
+    with open(annotated_output, "rb") as fh:
+        contents_annotated = fh.read()
+
+    with open(any_output, "rb") as fh:
+        contents_any = fh.read()
+    assert contents_annotated == contents_any
+
+
 def test_single_output():
     @task
     def my_task() -> str: