### Question:
WorkingDaysToDaysConverter { public Instant addWorkingDaysToInstant(Instant instant, Duration workingDays) { long days = convertWorkingDaysToDays(instant, workingDays.toDays(), ZeroDirection.ADD_DAYS); return instant.plus(Duration.ofDays(days)); } WorkingDaysToDaysConverter(boolean germanHolidaysEnabled, boolean corpusChristiEnabled);  WorkingDaysToDaysConverter(
      boolean germanHolidaysEnabled,
      boolean corpusChristiEnabled,
      Collection<CustomHoliday> customHolidays); Instant addWorkingDaysToInstant(Instant instant, Duration workingDays); Instant subtractWorkingDaysFromInstant(Instant instant, Duration workingDays); boolean hasWorkingDaysInBetween(Instant left, Instant right); boolean isWorkingDay(Instant referenceDate); boolean isWeekend(LocalDate dateToCheck); boolean isHoliday(LocalDate date); boolean isGermanHoliday(LocalDate date); @Override String toString();  }### Answer:
@Test void testConvertWorkingDaysToDaysForKarFreitag() { Instant gruenDonnerstag2018 = Instant.parse("2018-03-29T01:00:00.000Z"); Instant days = converter.addWorkingDaysToInstant(gruenDonnerstag2018, Duration.ofDays(0)); assertThat(days).isEqualTo(gruenDonnerstag2018.plus(0, ChronoUnit.DAYS)); days = converter.addWorkingDaysToInstant(gruenDonnerstag2018, Duration.ofDays(1)); assertThat(days).isEqualTo(gruenDonnerstag2018.plus(5, ChronoUnit.DAYS)); days = converter.addWorkingDaysToInstant(gruenDonnerstag2018, Duration.ofDays(2)); assertThat(days).isEqualTo(gruenDonnerstag2018.plus(6, ChronoUnit.DAYS)); }
@Test void testConvertWorkingDaysToDaysForHolidays() { Instant freitag0427 = Instant.parse("2018-04-27T19:00:00.000Z"); Instant days = converter.addWorkingDaysToInstant(freitag0427, Duration.ofDays(0)); assertThat(days).isEqualTo(freitag0427.plus(0, ChronoUnit.DAYS)); days = converter.addWorkingDaysToInstant(freitag0427, Duration.ofDays(1)); assertThat(days).isEqualTo(freitag0427.plus(3, ChronoUnit.DAYS)); days = converter.addWorkingDaysToInstant(freitag0427, Duration.ofDays(2)); assertThat(days).isEqualTo(freitag0427.plus(5, ChronoUnit.DAYS)); }