return singleton(elements[0]);
              }
            })
        .named("singleton")
        .withFeatures(
            CollectionFeature.SERIALIZABLE,
            CollectionFeature.ALLOWS_NULL_VALUES,
            CollectionSize.ONE)
        .suppressing(suppressForSingletonSet())
        .createTestSuite();
  }

  public Test testsForHashSet() {
    return SetTestSuiteBuilder.using(

import static com.google.common.collect.testing.Helpers.getMethod;
import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_QUERIES;
import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;

 * limitations under the License.
 */

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

import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.CollectionFeature.KNOWN_ORDER;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_ADD;

  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_VALUES})
  public void testPut_nullValueSupported() {
    assertNull("put(key, null) should return null", put(nullValueEntry));
    expectAdded(nullValueEntry);
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  public void testPut_nullValueUnsupported() {

  private static final Feature<?>[] FOR_MAP_FEATURES_ONE = {
    CollectionSize.ONE,
    ALLOWS_NULL_VALUES,
    SUPPORTS_REMOVE,
    CollectionFeature.SUPPORTS_ITERATOR_REMOVE
  };

  private static final Feature<?>[] FOR_MAP_FEATURES_ANY = {
    CollectionSize.ANY,
    ALLOWS_NULL_VALUES,
    SUPPORTS_REMOVE,
    CollectionFeature.SUPPORTS_ITERATOR_REMOVE,

            .withFeatures(CollectionSize.ANY, CollectionFeature.ALLOWS_NULL_VALUES)
            .named("Multisets.union")
            .createTestSuite());

    suite.addTest(
        MultisetTestSuiteBuilder.using(intersectionGenerator())
            .withFeatures(
                CollectionSize.ANY,
                CollectionFeature.ALLOWS_NULL_VALUES,
                CollectionFeature.KNOWN_ORDER)

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_VALUES;
import static com.google.common.collect.testing.features.MapFeature.SUPPORTS_PUT;
import static com.google.common.collect.testing.testers.ReflectionFreeAssertThrows.assertThrows;

                return singleton(elements[0]);
              }
            })
        .named("singleton")
        .withFeatures(
            CollectionFeature.SERIALIZABLE,
            CollectionFeature.ALLOWS_NULL_VALUES,
            CollectionSize.ONE)
        .suppressing(suppressForSingletonSet())
        .createTestSuite();
  }

  public Test testsForHashSet() {
    return SetTestSuiteBuilder.using(

    assertThrows(NullPointerException.class, () -> initMapWithNullKey());
  }

  @MapFeature.Require(ALLOWS_NULL_VALUES)
  @CollectionSize.Require(absent = ZERO)
  public void testCreateWithNullValueSupported() {
    initMapWithNullValue();
    expectContents(createArrayWithNullValue());
  }

  @MapFeature.Require(absent = ALLOWS_NULL_VALUES)
  @CollectionSize.Require(absent = ZERO)
  public void testCreateWithNullValueUnsupported() {

  @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)