public List<? extends Coder<?>> getElementCoders() {
    return elementCoders;
  }
@Test
  public void testGetElementCoders() {
    UnionCoder unionCoder = UnionCoder.of(ImmutableList.of(StringUtf8Coder.of(), DoubleCoder.of()));
    assertThat(unionCoder.getElementCoders().get(0), Matchers.equalTo(StringUtf8Coder.of()));
    assertThat(unionCoder.getElementCoders().get(1), Matchers.equalTo(DoubleCoder.of()));
  }