Add tests for hasAppointment in model manager

src/test/java/seedu/address/model/ModelManagerTest.java

@@ -6,6 +6,7 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static seedu.address.model.Model.PREDICATE_SHOW_ALL_PERSONS;
 import static seedu.address.testutil.Assert.assertThrows;
+import static seedu.address.testutil.TypicalAppointments.APPOINTMENT_1;
 import static seedu.address.testutil.TypicalAppointments.getTypicalAppointmentBook;
 import static seedu.address.testutil.TypicalPersons.ALICE;
 import static seedu.address.testutil.TypicalPersons.ALICE_P;
@@ -18,6 +19,7 @@
 import org.junit.jupiter.api.Test;
 
 import seedu.address.commons.core.GuiSettings;
+import seedu.address.model.appointment.Appointment;
 import seedu.address.model.person.NameContainsKeywordsPredicate;
 import seedu.address.model.person.Person;
 import seedu.address.testutil.AddressBookBuilder;
@@ -92,6 +94,26 @@ public void hasPerson_personInAddressBook_returnsTrue() {
         assertTrue(modelManager.hasPerson(ALICE));
     }
 
+    @Test
+    public void hasAppointment_nullAppointment_throwsNullPointerException() {
+        assertThrows(NullPointerException.class, () -> modelManager.hasAppointment((Appointment) null));
+    }
+
+    @Test
+    public void hasAppointment_appointmentNotInAppointmentBook_returnsFalse() {
+        assertFalse(modelManager.hasAppointment(APPOINTMENT_1));
+        assertFalse(modelManager.hasAppointment(APPOINTMENT_1.getAppointmentDescriptor(),
+            APPOINTMENT_1.getPerson()));
+    }
+
+    @Test
+    public void hasAppointment_appointmentInAppointmentBook_returnsTrue() {
+        modelManager.addAppointment(APPOINTMENT_1.getPerson(), APPOINTMENT_1.getAppointmentDescriptor());
+        assertTrue(modelManager.hasAppointment(APPOINTMENT_1));
+        assertTrue(modelManager.hasAppointment(APPOINTMENT_1.getAppointmentDescriptor(),
+            APPOINTMENT_1.getPerson()));
+    }
+
     @Test
     public void getFilteredPersonList_modifyList_throwsUnsupportedOperationException() {
         assertThrows(UnsupportedOperationException.class, () -> modelManager.getFilteredPersonList().remove(0));