DocMap docMap = new DocMap(parentMap);

        docMap.put("nullKey", null);
        assertTrue(docMap.containsKey("nullKey"));
        assertTrue(docMap.containsValue(null));
        assertNull(docMap.get("nullKey"));

        assertNull(docMap.put("nullKey", "newValue"));
        assertEquals("newValue", docMap.get("nullKey"));
    }

    public void test_map_interface_compliance() {

    }

    // Test getAsString with null value
    public void test_getAsStringWithNullValue() {
        dataStoreParams.put("nullKey", null);
        assertNull(dataStoreParams.getAsString("nullKey"));
    }

    // Test getAsString for non-existent key
    public void test_getAsStringNonExistentKey() {
        assertNull(dataStoreParams.getAsString("nonexistent"));
    }

    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);

  }

  public void testOfEntriesNull() {
    Entry<@Nullable Integer, Integer> nullKey = entry(null, 23);
    assertThrows(
        NullPointerException.class,
        () -> ImmutableBiMap.ofEntries((Entry<Integer, Integer>) nullKey));
    Entry<Integer, @Nullable Integer> nullValue =
        ImmutableBiMapTest.<@Nullable Integer>entry(23, null);
    assertThrows(

        .testEquals();
  }

  public void testOfEntriesNull() {
    Entry<@Nullable Integer, @Nullable Integer> nullKey = entry(null, 23);
    assertThrows(
        NullPointerException.class,
        () -> ImmutableMap.ofEntries((Entry<Integer, Integer>) nullKey));
    Entry<@Nullable Integer, @Nullable Integer> nullValue = entry(23, null);
    assertThrows(
        NullPointerException.class,

        try {
            WebApiUtil.setObject("validKey", "validValue");
            WebApiUtil.setObject("", "emptyKey");
            WebApiUtil.setObject("nullValue", null);
            WebApiUtil.setObject(null, "nullKey");
            WebApiUtil.setObject(null, null);
        } catch (Exception e) {
            fail("setObject should handle parameter validation gracefully: " + e.getMessage());
        }

    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;
          }
        });
  }