private void checkScan(int expectCellSize) throws IOException {
    Scan s = new Scan().withStartRow(row);
    ScannerContext.Builder contextBuilder = ScannerContext.newBuilder(true);
    ScannerContext scannerContext = contextBuilder.build();
    try (RegionScanner scanner = region.getScanner(s)) {
      List<Cell> kvs = new ArrayList<>();
      scanner.next(kvs, scannerContext);
      assertEquals(expectCellSize, kvs.size());
    }
  }
Test RegionTooBusyException thrown when region is busy
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegion.java