@Override
      public Boolean answer(InvocationOnMock invocation) throws Throwable {
        invocation.<CompactionContext> getArgument(0).compact(invocation.getArgument(2), null);
        return true;
      }
Test compaction priority management and multiple compactions per store (HBASE-8665).
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestCompaction.java