public V merge(
        final Integer key, final V value, final BiFunction<? super V, ? super V, ? extends V> remappingFunction)
    {
        return merge((int)key, value, remappingFunction);
    }
@Test
    void mergeThrowsNullPointerExceptionIfValueIsNull()
    {
        final int key = -9;
        final BiFunction<String, String, String> remappingFunction = (v1, v2) -> "NEW";

        assertThrowsExactly(NullPointerException.class, () -> cache.merge(key, null, remappingFunction));
    }