Fix wrong test assertions

Author: Ndiritu

tests/requests/test_batch_request_content.py

@@ -107,5 +107,5 @@ def test_serialize(batch_request_content):
     writer = Mock(spec=SerializationWriter)
     batch_request_content.serialize(writer)
     writer.write_collection_of_object_values.assert_called_once_with(
-        "requests", batch_request_content.requests
+        "requests", list(batch_request_content.requests.values())
     )

tests/requests/test_batch_request_item.py

@@ -96,13 +96,13 @@ def test_id_property(batch_request_item):
 def test_headers_property(batch_request_item):
     new_headers = {"Authorization": "Bearer token"}
     batch_request_item.headers = new_headers
-    assert batch_request_item.headers["Authorization"] == "Bearer token"
+    assert batch_request_item.headers["authorization"] == "Bearer token"
 
 
 def test_body_property(batch_request_item):
     new_body = StreamInterface(b'{"new_key": "new_value"}')
     batch_request_item.body = new_body
-    assert batch_request_item.body.read() == b'{"new_key": "new_value"}'
+    assert batch_request_item.body == b'{"new_key": "new_value"}'
 
 
 def test_method_property(batch_request_item):