text: """Tests for module db.utils."""
  
  import datetime
  
  from fastproject import db
  
  
  def test_updater_fields():
      # Fields and null fields.
      fields = ("username", "email", "first_name")
      null_fields = ("last_name", "last_login")
      new_values = db.updater_fields(
          fields,
          null_fields,
          username="pontiff_sulyvahn",
          email="ps@email.com",
          first_name="Sulyvahn",
          last_login=datetime.datetime(2018, 12, 15),
      )
      assert new_values == {
          "username": "pontiff_sulyvahn",
          "email": "ps@email.com",
          "first_name": "Sulyvahn",
          "last_name": None,
          "update_last_name": False,
          "last_login": datetime.datetime(2018, 12, 15),
          "update_last_login": True,
      }
      # Fields only.
      fields = ("username", "email", "first_name", "last_name")
      new_values = db.updater_fields(
          fields=fields,
          username="pontiff_sulyvahn",
          email="ps@email.com",
          first_name="Sulyvahn",
      )
      assert new_values == {
          "username": "pontiff_sulyvahn",
          "email": "ps@email.com",
          "first_name": "Sulyvahn",
          "last_name": None,
      }
      # Null fields only
      null_fields = ("last_login", "birthday")
      new_values = db.updater_fields(
          null_fields=null_fields,
          updater_flag_preffix="upt_",
          last_login=datetime.datetime(2018, 12, 15),
          birthday=None,
      )
      assert new_values == {
          "last_login": datetime.datetime(2018, 12, 15),
          "upt_last_login": True,
          "birthday": None,
          "upt_birthday": True,
      }
  