@Test
  public void testVectorCastLongToDouble() throws HiveException {
    VectorizedRowBatch b = TestVectorMathFunctions.getVectorizedRowBatchLongInDoubleOut();
    DoubleColumnVector resultV = (DoubleColumnVector) b.cols[1];
    b.cols[0].noNulls = true;
    VectorExpression expr = new CastLongToDouble(0, 1);
    expr.evaluate(b);
    Assert.assertEquals(2.0, resultV.vector[4], Double.MIN_VALUE);
  }
Test VectorExpression classes for vectorized implementations of type casts.
ql/src/test/org/apache/hadoop/hive/ql/exec/vector/expressions/TestVectorTypeCasts.java