@Test
  public void testForceSplit() throws Exception {
    byte[][] familyNames = new byte[][] { Bytes.toBytes("cf") };
    int[] rowCounts = new int[] { 6000 };
    int numVersions = ColumnFamilyDescriptorBuilder.DEFAULT_MAX_VERSIONS;
    int blockSize = 256;
    splitTest(null, familyNames, rowCounts, numVersions, blockSize, true);

    byte[] splitKey = Bytes.toBytes(3500);
    splitTest(splitKey, familyNames, rowCounts, numVersions, blockSize, true);
    // test regionSplitSync
    splitTest(splitKey, familyNames, rowCounts, numVersions, blockSize, false);
  }
Tests forcing split from client and having scanners successfully ride over split.
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAdmin1.java