### Question:
DetailViewModel implements ViewModel { public ReadOnlyStringProperty birthdayLabelTextProperty() { return birthday.getReadOnlyProperty(); }  void initialize(); Command getEditCommand(); Command getRemoveCommand(); Command getEmailLinkCommand(); ReadOnlyStringProperty nameLabelTextProperty(); ReadOnlyStringProperty birthdayLabelTextProperty(); ReadOnlyStringProperty roleDepartmentLabelTextProperty(); ReadOnlyStringProperty emailLabelTextProperty(); ReadOnlyStringProperty phoneLabelTextProperty(); ReadOnlyStringProperty mobileLabelTextProperty(); ReadOnlyStringProperty cityPostalcodeLabelTextProperty(); ReadOnlyStringProperty streetLabelTextProperty(); ReadOnlyStringProperty countrySubdivisionLabelTextProperty(); static final String OPEN_EDIT_CONTACT_DIALOG; }### Answer:
@Test public void testBirthdayLabelText() { luke.setBirthday(LocalDate.of(1951, 9, 25)); obi.setBirthday(null); selectedContact.set(null); assertThat(viewModel.birthdayLabelTextProperty()).hasValue(""); selectedContact.set(luke); assertThat(viewModel.birthdayLabelTextProperty()).hasValue("1951-09-25"); selectedContact.set(obi); assertThat(viewModel.birthdayLabelTextProperty()).hasValue(""); }