@Test
public void testFrontfill() {

  DoubleColumn col =
      (DoubleColumn)
          DoubleColumn.create(
                  "testCol",
                  new double[] {missing, missing, 0.181, 0.186, missing, missing, 0.181})
              .interpolate()
              .frontfill();
  assertArrayEquals(
      new double[] {missing, missing, 0.181, 0.186, 0.186, 0.186, 0.181}, col.asDoubleArray());
}