@Test
public void tinyContainer_addAll_fromOneElement() {

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