@Test
	public void testAsMapHeadHigher() {
		populateStore(-3, -1, 1, 3);

		assertEquals(3, doTestMap(map.headMap(3L, true), NavigableMap::higherKey, //
			NavigableMap::higherEntry, 1L).longValue());
		assertNull(doTestMap(map.headMap(1L, true), NavigableMap::higherKey,
			NavigableMap::higherEntry, 1L));
		assertNull(doTestMap(map.headMap(1L, false), NavigableMap::higherKey,
			NavigableMap::higherEntry, 1L));
		assertNull(doTestMap(map.headMap(-1L, false), NavigableMap::higherKey,
			NavigableMap::higherEntry, 1L));

		assertEquals(-3, doTestMap(rMap.headMap(-3L, true), NavigableMap::higherKey,
			NavigableMap::higherEntry, -1L).longValue());
		assertNull(doTestMap(rMap.headMap(-1L, true), NavigableMap::higherKey,
			NavigableMap::higherEntry, -1L));
		assertNull(doTestMap(rMap.headMap(-1L, false), NavigableMap::higherKey,
			NavigableMap::higherEntry, -1L));
		assertNull(doTestMap(rMap.headMap(1L, false), NavigableMap::higherKey,
			NavigableMap::higherEntry, -1L));
	}
This exists to verify behavior in {@link #testAsValuesSubIterator()}
Ghidra/Debug/ProposedUtils/src/test/java/ghidra/util/database/DBCachedObjectStoreTest.java