diff --git a/apps/transport/lib/transport/gtfs_diff.ex b/apps/transport/lib/transport/gtfs_diff.ex
index 4f4f4b6e8c..98c28e0d15 100644
--- a/apps/transport/lib/transport/gtfs_diff.ex
+++ b/apps/transport/lib/transport/gtfs_diff.ex
@@ -334,6 +334,7 @@ defmodule Transport.GTFSDiff do
     [headers | body]
     |> CSV.dump_to_stream()
     |> Stream.into(File.stream!(filepath))
+    |> Stream.run()
   end
 
   def apply_delete(file, diff, primary_key) do
@@ -410,11 +411,3 @@ defmodule Transport.GTFSDiff do
     |> IO.iodata_to_binary()
   end
 end
-
-# usage
-
-# unzip_1 = Transport.GTFSDiff.unzip("path/to/gtfs_1.zip")
-# unzip_2 = Transport.GTFSDiff.unzip("path/to/gtfs_2.zip")
-
-# diff = Transport.GTFSDiff.diff(unzip_1, unzip_2)
-# File.write!("diff_output.txt", diff |> Transport.GTFSDiff.dump_diff())
diff --git a/apps/transport/test/transport/gtfs_diff_test.exs b/apps/transport/test/transport/gtfs_diff_test.exs
index 7a76b9c101..09661aeabb 100644
--- a/apps/transport/test/transport/gtfs_diff_test.exs
+++ b/apps/transport/test/transport/gtfs_diff_test.exs
@@ -1,12 +1,6 @@
 defmodule Transport.GTFSDiffTest do
   use ExUnit.Case, async: true
 
-  defp unzip(path) do
-    zip_file = Unzip.LocalFile.open(path)
-    {:ok, unzip} = Unzip.new(zip_file)
-    unzip
-  end
-
   describe "GTFS Diff" do
     test "2 identical files" do
       unzip_1 = unzip("test/fixture/files/gtfs_diff/gtfs.zip")
@@ -128,4 +122,43 @@ defmodule Transport.GTFSDiffTest do
              ]
     end
   end
+
+  describe "dump_diff" do
+    test "empty diff, file is created" do
+      tmp_path = System.tmp_dir!() |> Path.join(Ecto.UUID.generate())
+      refute File.exists?(tmp_path)
+      Transport.GTFSDiff.dump_diff([], tmp_path)
+      assert File.exists?(tmp_path)
+
+      assert [["id", "file", "action", "target", "identifier", "initial_value", "new_value", "note"]] ==
+               read_csv(tmp_path)
+
+      File.rm(tmp_path)
+    end
+
+    test "simple diff" do
+      diff = [%{action: "delete", file: "stops.txt", id: 1, identifier: %{"stop_id" => "near1"}, target: "row"}]
+      tmp_path = System.tmp_dir!() |> Path.join(Ecto.UUID.generate())
+      refute File.exists?(tmp_path)
+      Transport.GTFSDiff.dump_diff(diff, tmp_path)
+      assert File.exists?(tmp_path)
+
+      assert [
+               ["id", "file", "action", "target", "identifier", "initial_value", "new_value", "note"],
+               ["1", "stops.txt", "delete", "row", ~s({"stop_id":"near1"}), "", "", ""]
+             ] == read_csv(tmp_path)
+
+      File.rm(tmp_path)
+    end
+  end
+
+  defp unzip(path) do
+    zip_file = Unzip.LocalFile.open(path)
+    {:ok, unzip} = Unzip.new(zip_file)
+    unzip
+  end
+
+  defp read_csv(filepath) do
+    filepath |> File.read!() |> NimbleCSV.RFC4180.parse_string(skip_headers: false)
+  end
 end