func TestFormattingOfTemperaturesSpecialValueOff(t *testing.T) {
    th := Thermostat{Measured: "253", Saving: "253", Goal: "253", Comfort: "253"}
    assert.Equal(t, "OFF", th.FmtMeasuredTemperature())
    assert.Equal(t, "OFF", th.FmtSavingTemperature())
    assert.Equal(t, "OFF", th.FmtGoalTemperature())