    @Test
    public void rate_should_return_99_when_period_is_100_and_time_is_399() {

        // GIVEN
        ConcretePeriodicRateGenerator periodicRateGenerator = new ConcretePeriodicRateGenerator(100);

        // WHEN
        double rate = periodicRateGenerator.getRate(TimeUnit.SECONDS.toNanos(399));

        // THEN
        Assert.assertEquals(99d, rate, DELTA);
    }