### Question:
UniquePropertyValidator implements ConstraintValidator<UniqueProperty, WithId<?>> { @Override public boolean isValid(final WithId<?> value, final ConstraintValidatorContext context) { if (value == null) { return true; } final PropertyAccessor bean = new BeanWrapperImpl(value); final String propertyValue = String.valueOf(bean.getPropertyValue(property)); @SuppressWarnings({"rawtypes", "unchecked"}) final Class<WithId> modelClass = (Class) value.getKind().modelClass; @SuppressWarnings("unchecked") final Set<String> ids = dataManager.fetchIdsByPropertyValue(modelClass, property, propertyValue); final boolean isUnique = ids.isEmpty() || value.getId().map(id -> ids.contains(id)).orElse(false); if (!isUnique) { context.disableDefaultConstraintViolation(); context.unwrap(HibernateConstraintValidatorContext.class).addExpressionVariable("nonUnique", propertyValue) .buildConstraintViolationWithTemplate(context.getDefaultConstraintMessageTemplate()) .addPropertyNode(property).addConstraintViolation(); } return isUnique; }  @Override void initialize(final UniqueProperty uniqueProperty); @Override boolean isValid(final WithId<?> value, final ConstraintValidatorContext context);  }### Answer:
@Test public void shouldAscertainPropertyUniqueness() { final HibernateConstraintValidatorContext context = mock(HibernateConstraintValidatorContext.class); when(context.unwrap(HibernateConstraintValidatorContext.class)).thenReturn(context); when(context.addExpressionVariable(eq("nonUnique"), anyString())).thenReturn(context); when(context.getDefaultConstraintMessageTemplate()).thenReturn("template"); final ConstraintViolationBuilder builder = mock(ConstraintViolationBuilder.class); when(context.buildConstraintViolationWithTemplate("template")).thenReturn(builder); when(builder.addPropertyNode(anyString())).thenReturn(mock(NodeBuilderCustomizableContext.class)); assertThat(validator.isValid(connection, context)).isEqualTo(validity); }