diff --git a/lib/onigumo.ex b/lib/onigumo.ex
index 979df75..5484b3f 100644
--- a/lib/onigumo.ex
+++ b/lib/onigumo.ex
@@ -19,7 +19,7 @@ defmodule Onigumo do
   end
 
   def download_url(url, root_path) do
-    file_name = Base.url_encode64(url, padding: false)
+    file_name = create_file_name(url)
     file_path = Path.join(root_path, file_name)
 
     url
@@ -54,4 +54,8 @@ defmodule Onigumo do
   defp http_client() do
     Application.get_env(:onigumo, :http_client)
   end
+
+  def create_file_name(url) do
+    Base.url_encode64(url, padding: false)
+  end
 end
diff --git a/test/onigumo_test.exs b/test/onigumo_test.exs
index 272ace8..4b526ef 100644
--- a/test/onigumo_test.exs
+++ b/test/onigumo_test.exs
@@ -17,7 +17,7 @@ defmodule OnigumoTest do
     download_result = Onigumo.download_url(input_url, tmp_dir)
     assert(download_result == :ok)
 
-    output_file_name = Base.url_encode64(input_url, padding: false)
+    output_file_name = Onigumo.create_file_name(input_url)
     output_path = Path.join(tmp_dir, output_file_name)
     read_output = File.read!(output_path)
     expected_output = body(input_url)
@@ -90,6 +90,17 @@ defmodule OnigumoTest do
     assert(read_output == response)
   end
 
+  test("create file name from URL") do
+    input_url = "https://onigumo.local/hello.html"
+    created_file_name = Onigumo.create_file_name(input_url)
+
+    expected_file_name = Base.url_encode64(input_url, padding: false)
+    assert(created_file_name == expected_file_name)
+
+    unexpected_file_name = Base.url_encode64(input_url, padding: true)
+    assert(created_file_name != unexpected_file_name)
+  end
+
   defp prepare_response(url) do
     %HTTPoison.Response{
       status_code: 200,