### Question:
Idempotence { List<String> removeSmallWords(List<String> input) { return input .map(String::trim) .filter(s -> s.length() >= 3); }    }### Answer:
@Test public void empty_empty() { assertThat(cut.removeSmallWords(List())).isEqualTo(List()); }
@Test public void keep_long_enough() { assertThat(cut.removeSmallWords(List("a", "bc", "def", "ghij"))).isEqualTo(List("def", "ghij")); }
@Test public void remove_all_small() { assertThat(cut.removeSmallWords(List(" a", "b", "c ", " de "))).isEqualTo(List()); }
@Test public void many_random() { assertThat(cut.removeSmallWords(List("hello", "", "wo rld ", " !!"))).isEqualTo(List("hello", "wo rld")); }