@Test
    @DisplayName("Test isValid with null context")
    void testIsValidWithNullContext() {
        // Arrange
        when(negotiationResponse.isValid(null, negotiationRequest)).thenReturn(false);

        // Act
        boolean result = negotiationResponse.isValid(null, negotiationRequest);

        // Assert
        assertFalse(result);
        verify(negotiationResponse).isValid(null, negotiationRequest);
    }

    @Test

            assertThrows(NullPointerException.class, () -> concreteImplementation.combine(null));
        }

        @Test
        @DisplayName("Should handle null in append")
        void testAppendWithNull() {
            // Test with mock
            doNothing().when(mockReferralData).append(null);
            assertDoesNotThrow(() -> mockReferralData.append(null));

        FavoriteLogCQ cq = new FavoriteLogCQ();
        if (queryLambda != null) {
            queryLambda.callback(cq);
        }
        FilterAggregationBuilder builder = regFilterA(name, cq.getQuery());
        if (opLambda != null) {
            opLambda.callback(builder);
        }
        if (aggsLambda != null) {
            FavoriteLogCA ca = new FavoriteLogCA();
            aggsLambda.callback(ca);

            if (labelValueMap != null) {
                return labelValueMap.get(value);
            }
            return null;
        }).orElse(value);
    }

    /**
     * Converts a Long timestamp to a Date object.
     *
     * @param value the timestamp in milliseconds
     * @return Date object representing the timestamp, or null if value is null
     */

    }

    /**
     * Tests the isCredentialTypeCorrect method with a null byte array.
     * This test is indirect as the constructor would throw an exception.
     * We can't instantiate the class with null, so we can't directly test this method's behavior with null.
     * However, the constructor logic `!isCredentialTypeCorrect()` covers this.
     * If `new PacCredentialType(null)` throws, it implies `isCredentialTypeCorrect()` returned false for null.

    }

    private boolean determineVersionMatch(String version) {
        String test = version;
        boolean reverse = false;

        if (test.startsWith("!")) {
            reverse = true;
            test = test.substring(1);
        }

        boolean result = Os.OS_VERSION.equals(test);

        if (reverse) {

    for (LoadingCache<Object, Object> cache : caches()) {
      Set<Object> keys = cache.asMap().keySet();
      assertFalse(keys.remove(null));
      assertFalse(keys.remove(6));
      assertFalse(keys.remove(-6));
      assertFalse(keys.removeAll(asList(null, 0, 15, 1500)));
      assertFalse(keys.retainAll(asList(null, 0, 15, 1500)));
      checkEmpty(keys);
      checkEmpty(cache);
    }
  }

  public void testKeySet_remove() {

      return;
    }

    map.put(null, unmappedValue);
    assertEquals(unmappedValue, map.get(null));
    assertTrue(map.containsKey(null));
    Entry<@Nullable K, V> entry = mapEntry(null, unmappedValue);
    assertTrue(entrySet.remove(entry));
    assertNull(map.get(null));
    assertFalse(map.containsKey(null));
  }

  public void testEntrySetRemoveNullKeyMissing() {

                break;
            }
        }
        if (authMethod == null) {
            return null;
        }
        NtlmMessage message = authorization != null ? new Type2Message(Base64.decode(authorization)) : null;
        reconnect();
        if (message == null) {
            message = new Type1Message();
            if (LM_COMPATIBILITY > 2) {

            return null;
        }
        synchronized (this.addressCache) {
            CacheEntry entry = this.addressCache.get(hostName);
            if (entry != null && entry.expiration < System.currentTimeMillis() && entry.expiration >= 0) {
                entry = null;
            }
            return entry != null ? entry.address : null;
        }
    }

    int getNextNameTrnId() {