}
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEYS)
  public void testPutIfAbsent_nullKeyUnsupported() {
    assertThrows(NullPointerException.class, () -> getMap().putIfAbsent(null, v3()));
    expectUnchanged();
    expectNullKeyMissingWhenNullKeysUnsupported(
        "Should not contain null key after unsupported putIfAbsent(null, value)");
  }

  @SuppressWarnings("nullness") // test of a bogus call
  public void testNullListener() {
    assertThrows(NullPointerException.class, () -> future.addListener(null, directExecutor()));
  }

  @SuppressWarnings("nullness") // test of a bogus call
  public void testNullExecutor() {
    assertThrows(NullPointerException.class, () -> future.addListener(doNothing(), null));
  }

  @SuppressWarnings("nullness") // test of a bogus call

    assertThrows(
        NullPointerException.class, () -> builder.put(immutableCell((Character) null, 1, "foo")));
    assertThrows(
        NullPointerException.class, () -> builder.put(immutableCell('a', (Integer) null, "foo")));
    assertThrows(
        NullPointerException.class, () -> builder.put(immutableCell('a', 1, (String) null)));
  }

        @DisplayName("Null delegate causes NullPointerException during construction")
        void nullDelegate_throwsNPE() throws Exception {
            SmbFile parent = newParent();
            assertThrows(NullPointerException.class, () -> new ShareEnumIterator(parent, null, null));
        }

        @Test
        @DisplayName("Null parent with non-empty iterator causes NullPointerException during adapt")

  public void testContainsEntryNullDisallowedBecauseKeyQueriesDisallowed() {
    assertThrows(NullPointerException.class, () -> multimap().containsEntry(null, v3()));
  }

  @MapFeature.Require(absent = ALLOWS_NULL_VALUE_QUERIES)
  public void testContainsEntryNullDisallowedBecauseValueQueriesDisallowed() {
    assertThrows(NullPointerException.class, () -> multimap().containsEntry(k3(), null));
  }

    EqualsTester tester = new EqualsTester();
    assertThrows(NullPointerException.class, () -> tester.addEqualityGroup((Object[]) null));
  }

  public void testNullObjectInEqualityGroup() {
    EqualsTester tester = new EqualsTester();
    NullPointerException e =
        assertThrows(NullPointerException.class, () -> tester.addEqualityGroup(1, null, 3));
    assertErrorMessage(e, "at index 1");
  }

    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEYS)
  public void testPutIfAbsent_nullKeyUnsupported() {
    assertThrows(NullPointerException.class, () -> getMap().putIfAbsent(null, v3()));
    expectUnchanged();
    expectNullKeyMissingWhenNullKeysUnsupported(
        "Should not contain null key after unsupported putIfAbsent(null, value)");
  }

    }

    @Test
    @DisplayName("openConnection with null URL throws NullPointerException")
    void testOpenConnection_NullInput() {
        // Arrange
        Handler handler = newHandlerWith(mockCtx);

        // Act & Assert
        assertThrows(NullPointerException.class, () -> handler.openConnection(null), "Null URL should throw NPE");

        }
    }

    @Test
    void testNullHandling() {
        assertThrows(NullPointerException.class, () -> Sources.fromPath(null));
        assertThrows(NullPointerException.class, () -> Sources.buildSource(null));
        assertThrows(NullPointerException.class, () -> Sources.resolvedSource(null, "modelId"));
    }

    assertThat(Stream.of(1).collect(toOptional())).hasValue(1);
  }

  public void testToOptionalNull() {
    Stream<@Nullable Object> stream = Stream.of((Object) null);
    assertThrows(NullPointerException.class, () -> stream.collect(toOptional()));
  }

  public void testToOptionalMultiple() {
    IllegalArgumentException expected =