return union(emptySet(), emptySet());
                  }
                })
            .named("empty U empty")
            .withFeatures(CollectionSize.ZERO, CollectionFeature.ALLOWS_NULL_VALUES)
            .createTestSuite());

    suite.addTest(
        SetTestSuiteBuilder.using(
                new TestStringSetGenerator() {
                  @Override

  @CollectionFeature.Require(SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  public void testAdd_supportedPresent() {
    assertFalse("add(present) should return false", getSet().add(e0()));
    expectUnchanged();
  }

  @CollectionFeature.Require(value = {SUPPORTS_ADD, ALLOWS_NULL_VALUES})
  @CollectionSize.Require(absent = ZERO)
  public void testAdd_supportedNullPresent() {
    E[] array = createArrayWithNullElement();

import static com.google.common.collect.testing.Helpers.copyToList;
import static com.google.common.collect.testing.Helpers.copyToSet;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.MapFeature.SUPPORTS_PUT;

import com.google.common.annotations.GwtCompatible;

  @CollectionFeature.Require(ALLOWS_NULL_VALUES)
  @CollectionSize.Require(absent = ZERO)
  public void testCreateWithNull_supported() {
    E[] array = createArrayWithNullElement();
    collection = getSubjectGenerator().create(array);
    expectContents(array);
  }

  @CollectionFeature.Require(absent = ALLOWS_NULL_VALUES)
  @CollectionSize.Require(absent = ZERO)
  public void testCreateWithNull_unsupported() {

    for (long value : TEST_LONGS) {
      BigInteger expected =
          (value >= 0)
              ? BigInteger.valueOf(value)
              : BigInteger.valueOf(value).add(BigInteger.ZERO.setBit(64));
      assertWithMessage(UnsignedLongs.toString(value))
          .that(UnsignedLong.fromLongBits(value).bigIntegerValue())
          .isEqualTo(expected);
    }
  }

  public void testValueOfLong() {

import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.google.MultisetFeature.ENTRIES_ARE_VIEWS;
import static java.util.Collections.singleton;

import com.google.common.annotations.GwtCompatible;

   * @return the count of the element before the operation; possibly zero
   * @throws IllegalArgumentException if {@code count} is negative
   * @throws NullPointerException if {@code element} is null and this implementation does not permit
   *     null elements. Note that if {@code count} is zero, the implementor may optionally return
   *     zero instead.
   */
  @CanIgnoreReturnValue

 */

package com.google.common.collect.testing.testers;

import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEY_QUERIES;

 * limitations under the License.
 */

package com.google.common.collect.testing.google;

import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEY_QUERIES;

package com.google.common.collect.testing.google;

import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_ITERATOR_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEY_QUERIES;