### Question:
DoubleDistributionSummary implements Meter { public void record(double amount) { if (amount >= 0.0) { add(totalAmount, amount); add(totalOfSquares, amount * amount); max(max, amount); count.incrementAndGet(); lastUpdateTime.set(clock.wallTime()); } } DoubleDistributionSummary(Clock clock, Id id, long resetFreq); static DoubleDistributionSummary get(Id id); @Override Id id(); @Override boolean hasExpired(); @Override Iterable<Measurement> measure(); void record(double amount); long count(); double totalAmount();  }### Answer:
@Test public void testRecord() { DoubleDistributionSummary t = newInstance(); t.record(42.0); Assertions.assertEquals(t.count(), 1L); Assertions.assertEquals(t.totalAmount(), 42.0, 1e-12); }