### Question:
DefaultPlaceholderTimer extends AbstractDefaultPlaceholderMeter<Timer> implements Timer { @Override public void record(long amount, TimeUnit unit) { resolveToCurrentMeter().record(amount, unit); } DefaultPlaceholderTimer(PlaceholderId id, Registry registry); @Override void record(long amount, TimeUnit unit); @Override T record(Callable<T> f); @Override void record(Runnable f); @Override long count(); @Override long totalTime();  }### Answer:
@Test public void testRecord() { String[] tagValue = new String[] { "default" }; Timer timer = factory.timer(factory.createId("testRecord", Collections.singleton(new TestTagFactory(tagValue)))); timer.record(42, TimeUnit.MILLISECONDS); Assertions.assertEquals("testRecord:tag=default", timer.id().toString()); Assertions.assertEquals(timer.count(), 1L); Assertions.assertEquals(42000000L, timer.totalTime()); tagValue[0] = "value2"; Assertions.assertEquals("testRecord:tag=value2", timer.id().toString()); Assertions.assertEquals(0L, timer.count()); Assertions.assertEquals(0L, timer.totalTime()); }
@Test public void testMeasure() { Timer timer = factory.timer(factory.createId("testMeasure")); timer.record(42, TimeUnit.MILLISECONDS); clock.setWallTime(3712345L); for (Measurement m : timer.measure()) { Assertions.assertEquals(m.timestamp(), 3712345L); if (m.id().equals(timer.id().withTag(Statistic.count))) { Assertions.assertEquals(1.0, m.value(), 0.1e-12); } else if (m.id().equals(timer.id().withTag(Statistic.totalTime))) { Assertions.assertEquals(42e6, m.value(), 0.1e-12); } else { Assertions.fail("unexpected id: " + m.id()); } } }