### Question:
DefaultPlaceholderGauge extends AbstractDefaultPlaceholderMeter<Gauge> implements Gauge { @Override public double value() { return resolveToCurrentMeter().value(); } DefaultPlaceholderGauge(PlaceholderId id, Registry registry); @Override void set(double value); @Override double value();  }### Answer:
@Test public void testInit() { Gauge g = new DefaultPlaceholderGauge(new DefaultPlaceholderId("unused", registry), registry); Assertions.assertEquals(g.value(), Double.NaN, 1e-12); }