svoid test_AllOnAll() {
  for (bool variation : falseTrue()) {
    new AllOnAll<S, Int> aoa;
    aoa.newA("one");
    assertNullVerbose(aoa.next());
    aoa.newB(1);
    assertEqualsVerbose(pair("one", 1), aoa.next());
    assertNullVerbose(aoa.next());
    aoa.newB(2);
    if (!variation) aoa.newA("two");
    assertEqualsVerbose(pair("one", 2), aoa.next());
    if (variation) {
      assertNullVerbose(aoa.next());
      aoa.newA("two");
    }
    assertEqualsVerbose(pair("two", 1), aoa.next());
    assertEqualsVerbose(pair("two", 2), aoa.next());
    assertNullVerbose(aoa.next());
  }
  
  new AllOnAll<S, Int> aoa;
  aoa.newA("one");
  aoa.newB(1);
  aoa.newA("two");
  aoa.newB(2);
  assertEqualsVerbose(pair("one", 1), aoa.next());
  assertEqualsVerbose(pair("two", 1), aoa.next());
  assertEqualsVerbose(pair("one", 2), aoa.next());
  assertEqualsVerbose(pair("two", 2), aoa.next());
  assertNullVerbose(aoa.next());
}