### Question:
Invariant { boolean isNewYearEve(LocalDate date) { return date.getDayOfMonth() == 31 && date.getMonthValue() == 12; }    }### Answer:
@Test public void _2018_12_31() { assertThat(cut.isNewYearEve(LocalDate.of(2018, 12, 31))).isTrue(); }
@Test public void _1989_12_31() { assertThat(cut.isNewYearEve(LocalDate.of(1989, 12, 31))).isTrue(); }
@Test public void _2018_12_25() { assertThat(cut.isNewYearEve(LocalDate.of(2018, 12, 25))).isFalse(); }
@Test public void _2018_08_31() { assertThat(cut.isNewYearEve(LocalDate.of(2018, 8, 31))).isFalse(); }