[Streaming] Streaming Python API (#6755)

streaming/python/tests/test_function.py

@@ -0,0 +1,22 @@
+from ray.streaming import function
+from ray.streaming.runtime import gateway_client
+
+
+def test_get_simple_function_class():
+    simple_map_func_class = function._get_simple_function_class(
+        function.MapFunction)
+    assert simple_map_func_class is function.SimpleMapFunction
+
+
+class MapFunc(function.MapFunction):
+    def map(self, value):
+        return str(value)
+
+
+def test_load_function():
+    # function_bytes, module_name, class_name, function_name,
+    # function_interface
+    descriptor_func_bytes = gateway_client.serialize(
+        [None, __name__, MapFunc.__name__, None, "MapFunction"])
+    func = function.load_function(descriptor_func_bytes)
+    assert type(func) is MapFunc