@Test
void getDouble() {

  String[] words = {"foo", "bar", "larry", "foo", "lion", null, "ben", "tiger", "bar"};
  StringColumn wordColumn = StringColumn.create("words", words);
  double[] expected = new double[] {0.0, 1.0, 2.0, 0.0, 3.0, 4.0, 5.0, 6.0, 1.0};
  double[] result = new double[words.length];
  for (int i = 0; i < words.length; i++) {
    result[i] = wordColumn.getDouble(i);
  }
  assertArrayEquals(expected, result, 0.000_000_1);
}