write first test and let changeset errors return error json in controller

test/entendu_web/controllers/links_controller_test.exs

@@ -0,0 +1,27 @@
+defmodule EntenduWeb.ErrorViewTest do
+  use EntenduWeb.ConnCase, async: true
+
+  # Bring render/3 and render_to_string/3 for testing custom views
+  import Phoenix.View
+
+  test "renders 404.html" do
+    assert render_to_string(EntenduWeb.ErrorView, "404.html", []) == "Not Found"
+  end
+
+  test "just endpoint creates a link with valid attrs", %{conn: conn} do
+    params = %{
+      "text_content" => "some gibberish",
+      "filename" => "more gibberish"
+    }
+
+    conn = post(conn, Routes.link_path(conn, :just), params)
+
+    response = json_response(conn, 201)
+
+    assert %{
+             "id" => _link_id,
+             "text_content" => "some gibberish",
+             "filename" => "more gibberish"
+           } = response
+  end
+end