public Counter counter(String name) {
        return getOrAdd(name, MetricBuilder.COUNTERS);
    }
@Test
    public void accessingACounterRegistersAndReusesTheCounter() {
        final Counter counter1 = registry.counter("thing");
        final Counter counter2 = registry.counter("thing");

        assertThat(counter1)
                .isSameAs(counter2);

        verify(listener).onCounterAdded("thing", counter1);
    }