new TestStringMapGenerator() {
              @Override
              protected Map<String, String> create(Entry<String, String>[] entries) {
                return singletonMap(entries[0].getKey(), entries[0].getValue());
              }
            })
        .named("singletonMap")
        .withFeatures(
            MapFeature.ALLOWS_NULL_KEYS,
            MapFeature.ALLOWS_NULL_VALUES,

        "Should not contain null after unsupported putIfAbsent(present, null)");
  }

  @CanIgnoreReturnValue
  private V putIfAbsent(Entry<K, V> entry) {
    return getMap().putIfAbsent(entry.getKey(), entry.getValue());
  }

  public void testPut_nullValueSupported() {
    Entry<K, V> nullValueEntry = entry(k3(), null);
    assertNull(
        "putIfAbsent(key, null) should return null",
        getMap().putIfAbsent(nullValueEntry.getKey(), nullValueEntry.getValue()));
    expectAdded(nullValueEntry);
  }

    void setReleaseUpdatePolicy(ArtifactRepositoryPolicy policy);

    ArtifactRepositoryLayout getLayout();

    void setLayout(ArtifactRepositoryLayout layout);

    String getKey();

    @Deprecated
    boolean isUniqueVersion();

    @Deprecated
    boolean isBlacklisted();

    @Deprecated
    void setBlacklisted(boolean blackListed);

    /**

    assertNull("put(null, null) should return null", put(nullKeyValueEntry));
    expectAdded(nullKeyValueEntry);
  }

  @CanIgnoreReturnValue
  private V put(Entry<K, V> entry) {
    return getMap().put(entry.getKey(), entry.getValue());
  }

  /**
   * Returns the {@link Method} instance for {@link #testPut_nullKeyUnsupported()} so that tests of
   * {@link java.util.TreeMap} can suppress it with {@code

                                                                logger.debug("Skipping interpolation of field: " + field
                                                                        + " (key: " + entry.getKey() + ") in: "
                                                                        + cls.getName()
                                                                        + "; it is an unmodifiable collection.");

        if (headers != null) {
            // Mock by header name
            for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
                when(conn.getHeaderField(entry.getKey())).thenReturn(entry.getValue().get(0));
            }

            // Mock by index - getHeaderField(int)
            // Index 0 is status line, then headers in order
            int index = 1;

                    for (Object object : elements) {
                      Entry<Class, Impl> entry = (Entry<Class, Impl>) object;
                      map.putInstance(entry.getKey(), entry.getValue());
                    }
                    return (Map) map;
                  }
                })
            .named("MutableClassToInstanceMap")
            .withFeatures(

            return size;
        }
        if (obj instanceof Map<?, ?>) {
            long size = 0;
            for (final Map.Entry<?, ?> entry : ((Map<?, ?>) obj).entrySet()) {
                size += sizeOf(entry.getKey());
                size += sizeOf(entry.getValue());
            }
            return size;
        }
        return 16L;
    }

          Map.Entry<E, Integer> mapEntry = backingEntries.next();
          return new Multisets.AbstractEntry<E>() {
            @Override
            public E getElement() {
              return mapEntry.getKey();
            }

            @Override
            public int getCount() {
              Integer frequency = backingMap.get(getElement());
              return (frequency == null) ? 0 : frequency;