public static Builder builder() {
    return new Builder();
  }
@Test
  public void testSetPlatforms_emptyPlatformsSet() {
    try {
      ContainerBuildPlan.builder().setPlatforms(Collections.emptySet());
      Assert.fail();
    } catch (IllegalArgumentException ex) {
      Assert.assertEquals("platforms set cannot be empty", ex.getMessage());
    }
  }