Add PhoenixTest case

test/mihainator_web/upload_live_test.exs

@@ -0,0 +1,14 @@
+defmodule MihainatorWeb.UploadLiveTest do
+  @moduledoc false
+
+  use MihainatorWeb.ConnCase
+
+  test "calender has markings for interaction days", %{conn: conn} do
+    conn
+    |> visit("/")
+    |> upload("CSV file", "data/test.csv")
+    |> click_button("Upload")
+    |> assert_has("button.bg-green-300")
+    |> assert_has("button.bg-red-300")
+  end
+end