*/
  protected int getNullLocation() {
    return getNumElements() / 2;
  }

  protected MinimalCollection<E> createDisjointCollection() {
    return MinimalCollection.of(e3(), e4());
  }

  protected MinimalCollection<E> emptyCollection() {
    return MinimalCollection.<E>of();
  }

  protected final E e0() {
    return samples.e0();
  }

  protected final E e1() {

  }

  public void testCopyOf_collection_empty() {
    Collection<String> c = MinimalCollection.of();
    Set<String> set = copyOf(c);
    assertEquals(Collections.<String>emptySet(), set);
    assertSame(this.<String>of(), set);
  }

  public void testCopyOf_collection_oneElement() {
    Collection<String> c = MinimalCollection.of("a");
    Set<String> set = copyOf(c);
    assertEquals(singleton("a"), set);
  }

  }

  public void testCopyOf_collection_empty() {
    Collection<String> c = MinimalCollection.of();
    Multiset<String> multiset = ImmutableMultiset.copyOf(c);
    assertTrue(multiset.isEmpty());
  }

  public void testCopyOf_collection_oneElement() {
    Collection<String> c = MinimalCollection.of("a");
    Multiset<String> multiset = ImmutableMultiset.copyOf(c);

      assertFalse(message, getMap().containsValue(null));
    } catch (NullPointerException tolerated) {
      // Tolerated
    }
  }

  @Override
  protected MinimalCollection<Entry<K, V>> createDisjointCollection() {
    return MinimalCollection.of(e3(), e4());
  }

  protected int getNumEntries() {
    return getNumElements();
  }

  protected Collection<Entry<K, V>> getSampleEntries(int howMany) {

 * can be used in the testers.
 *
 * @author Regina O'Dell
 */
@GwtCompatible
@NullMarked
public class MinimalSet<E extends @Nullable Object> extends MinimalCollection<E> implements Set<E> {

  @SuppressWarnings("unchecked") // empty Object[] as E[]
  public static <E extends @Nullable Object> MinimalSet<E> of(E... contents) {

 * can be used in the testers.
 *
 * @author Regina O'Dell
 */
@GwtCompatible
@NullMarked
public class MinimalSet<E extends @Nullable Object> extends MinimalCollection<E> implements Set<E> {

  @SuppressWarnings("unchecked") // empty Object[] as E[]
  public static <E extends @Nullable Object> MinimalSet<E> of(E... contents) {

      assertFalse(message, getMap().containsValue(null));
    } catch (NullPointerException tolerated) {
      // Tolerated
    }
  }

  @Override
  protected MinimalCollection<Entry<K, V>> createDisjointCollection() {
    return MinimalCollection.of(e3(), e4());
  }

  protected int getNumEntries() {
    return getNumElements();
  }

  protected Collection<Entry<K, V>> getSampleEntries(int howMany) {