@Test
  public void testWALProviders() throws IOException {
    Configuration conf = new Configuration();
    WALFactory walFactory = new WALFactory(conf, this.currentServername.toString());
    assertEquals(walFactory.getWALProvider().getClass(), walFactory.getMetaProvider().getClass());

    // if providers are not set and do not enable SyncReplicationWALProvider
    walFactory = new WALFactory(conf, this.currentServername, null);
    assertEquals(walFactory.getWALProvider().getClass(), walFactory.getMetaProvider().getClass());
  }
A loaded WAL coprocessor won't break existing WAL test cases.
hbase-server/src/test/java/org/apache/hadoop/hbase/wal/TestWALFactory.java