assertSame(map, ImmutableClassToInstanceMap.copyOf(map));
  }

  public void testCopyOf_map_nulls() {
    Map<Class<? extends Number>, Number> nullKey = singletonMap(null, (Number) 1.0);
    assertThrows(NullPointerException.class, () -> ImmutableClassToInstanceMap.copyOf(nullKey));

    Map<? extends Class<? extends Number>, Number> nullValue = singletonMap(Number.class, null);

    Set<Feature<?>> inverseFeatures = new HashSet<>(mapFeatures);

    boolean nullKeys = inverseFeatures.remove(MapFeature.ALLOWS_NULL_KEYS);
    boolean nullValues = inverseFeatures.remove(MapFeature.ALLOWS_NULL_VALUES);

    if (nullKeys) {
      inverseFeatures.add(MapFeature.ALLOWS_NULL_VALUES);
    }
    if (nullValues) {

FIELD com.google.common.util.concurrent.ExecutionSequencer.ThreadConfinedTaskQueue.nextExecutor com.google.common.util.concurrent.ExecutionSequencer.TaskNonReentrantExecutor
# Real cycle, but the runningState field is null'ed on completion of the future.
FIELD com.google.common.util.concurrent.AggregateFuture.runningState
FIELD java.util.AbstractMap.keySet com.google.common.collect.AbstractMapBasedMultimap.NavigableKeySet

          subArray.contains(expectedSubArray[i]));
    }
    assertNull(
        "The array element immediately following the end of the collection should be nulled",
        array[getNumElements()]);
    // array[getNumElements() + 1] might or might not have been nulled
  }

  @CollectionFeature.Require(KNOWN_ORDER)
  public void testToArray_oversizedArray_ordered() {

            T[] result = super.toArray(array);
            if (size() < result.length) {
              // It works around a GWT bug where elements after last is not
              // properly null'ed.
              @Nullable Object[] unsoundlyCovariantArray = result;
              unsoundlyCovariantArray[size()] = null;
            }
            return result;
          }
        });
  }