### Question:
BlockExplorers { public static List<BlockExplorer> getAll() { return allBlockExplorers; } private  BlockExplorers(); static List<BlockExplorer> getAll(); static Optional<BlockExplorer> getBlockExplorerById(String id); static BlockExplorer getDefaultBlockExplorer();  }### Answer:
@Test public void testGetAll() { Collection<BlockExplorer> allBlockExplorers = BlockExplorers.getAll(); Iterator<BlockExplorer> iterator = allBlockExplorers.iterator(); assertThat(iterator.next() instanceof BitEasyComBlockExplorer).isTrue(); assertThat(iterator.next() instanceof BitPayComBlockExplorer).isTrue(); assertThat(iterator.next() instanceof BlockChainInfoBlockExplorer).isTrue(); assertThat(iterator.next() instanceof BlockonomicsBlockExplorer).isTrue(); assertThat(iterator.next() instanceof BlockrIoBlockExplorer).isTrue(); assertThat(iterator.next() instanceof BlockTrailComBlockExplorer).isTrue(); assertThat(iterator.next() instanceof SmartBitComAuBlockExplorer).isTrue(); assertThat(iterator.hasNext()).isFalse(); }