@Test
  public void testConcurrentWrites() throws Exception {
    // Run the WPE tool with three threads writing 3000 edits each concurrently.
    // When done, verify that all edits were written.
    int errCode =
      WALPerformanceEvaluation.innerMain(new Configuration(TEST_UTIL.getConfiguration()),
        new String[] { "-threads", "3", "-verify", "-noclosefs", "-iterations", "3000" });
    assertEquals(0, errCode);
  }
Write to a log file with three concurrent threads and verifying all data is written.
hbase-diagnostics/src/test/java/org/apache/hadoop/hbase/wal/TestFSHLogProviderWithConcurrentWrites.java