@Test
    final void testUpdateWithNullThenDataThenData() {
        Bucket first = new Bucket();
        populateDimensionLessValue("one", first, 2);
        cache.updateDimensionPersistence(null, first);
        Bucket second = new Bucket();
        populateDimensionLessValue("other", second, 3);
        cache.updateDimensionPersistence(first, second);
        Collection<String> names = second.getAllMetricNames();
        assertEquals(2, names.size());
        assertTrue(names.contains("one"));
        assertTrue(names.contains("other"));
    }
Functional test for point persistence layer.

@author Steinar Knutsen
container-core/src/test/java/com/yahoo/metrics/simple/DimensionsCacheTest.java