@Udf
  public int instr(final String str, final String substring) {
    return instr(str, substring, 1);
  }
@Test
  public void shouldReturnZeroOnNullValue() {
    assertThat(udf.instr(null, "OR"), is(0));
    assertThat(udf.instr(null, "OR", 1), is(0));
    assertThat(udf.instr(null, "OR", 1, 1), is(0));
    assertThat(udf.instr("CORPORATE FLOOR", null, 1), is(0));
    assertThat(udf.instr("CORPORATE FLOOR", null, 1, 1), is(0));
  }