@Test public void getOrCreate_whenSomeReferencesAreCleared() {

  map.putIfProbablyAbsent(key, "1");
  pretendGCHappened();
  map.putIfProbablyAbsent(key, "1");
  // we'd expect two distinct entries..
  assertThat(map.target.keySet())
    .extracting(WeakReference::get)
    .containsExactlyInAnyOrder(null, key);
}