@Test
public void tinyContainer_addAll_fromTwoElements() {

  TinyContainer<String> source = Stream.of("a", "b").collect(toTinyContainer());
  assertThat(Stream.<String>empty().collect(toTinyContainer()).addAll(source).when((x, y) -> true, (a, b) -> a + b))
      .hasValue("ab");
  assertThat(Stream.of("c").collect(toTinyContainer()).addAll(source).size())
      .isEqualTo(3);
  assertThat(Stream.of("c", "d").collect(toTinyContainer()).addAll(source).size())
      .isEqualTo(4);
  assertThat(Stream.of("c", "d", "e").collect(toTinyContainer()).addAll(source).size())
      .isEqualTo(5);
}