tests: add autocomplete system tests.

test/test_helpers/system_test_helper.rb

@@ -0,0 +1,9 @@
+module SystemTestHelper
+  def signup(name, password: "password")
+    visit new_user_path
+    fill_in "Name", with: name
+    fill_in "Password", with: password
+    fill_in "Password confirmation", with: password
+    click_button "Sign up"
+  end
+end