Add tests for supporting Iterable collections across the lib

Replicates graphql/graphql-js@61c2b01

Author: Cito

tests/utilities/test_ast_from_value.py

@@ -207,6 +207,21 @@ def converts_list_values_to_list_asts():
             values=[EnumValueNode(value="HELLO"), EnumValueNode(value="GOODBYE")]
         )
 
+        def list_generator():
+            yield 1
+            yield 2
+            yield 3
+
+        assert ast_from_value(list_generator(), GraphQLList(GraphQLInt)) == (
+            ListValueNode(
+                values=[
+                    IntValueNode(value="1"),
+                    IntValueNode(value="2"),
+                    IntValueNode(value="3"),
+                ]
+            )
+        )
+
     def converts_list_singletons():
         assert ast_from_value("FOO", GraphQLList(GraphQLString)) == StringValueNode(
             value="FOO"

tests/utilities/test_coerce_input_value.py

@@ -285,6 +285,15 @@ def returns_no_error_for_a_valid_input():
             result = _coerce_value([1, 2, 3], TestList)
             assert expect_value(result) == [1, 2, 3]
 
+        def returns_no_error_for_a_valid_iterable_input():
+            def list_generator():
+                yield 1
+                yield 2
+                yield 3
+
+            result = _coerce_value(list_generator(), TestList)
+            assert expect_value(result) == [1, 2, 3]
+
         def returns_an_error_for_an_invalid_input():
             result = _coerce_value([1, "b", True, 4], TestList)
             assert expect_errors(result) == [