@Test
    void validateValueInternal_Date_range() {
        setupValues(null, Locale.ENGLISH);
        java.util.Calendar calFrom = GregorianCalendar.getInstance();
        calFrom.set(2019, 6, 23);
        java.util.Calendar calTo = GregorianCalendar.getInstance();
        calTo.set(2019, 6, 30);

        when(datePicker.getSelectionMode()).thenReturn("range");
        List<Date> range = Arrays.asList(calFrom.getTime(), calTo.getTime());
        DatePicker.ValidationResult validationResult = datePicker.validateValueInternal(context, range);
        assertTrue(datePicker.isValid());
        assertEquals(DatePicker.ValidationResult.OK, validationResult);
    }
Invalid {@link ResolverStyle}. The date 02/30/2019 is silently parsed to
02/28/2019 as default value 'SMART' is used.
primefaces/src/test/java/org/primefaces/component/datepicker/DatePickerTest.java