Add unit tests for datepicker.component (#12592)

Co-authored-by: Jason Qiu <jason_qiu@hotmail.com>

src/web/app/components/datepicker/datepicker.component.spec.ts

@@ -1,6 +1,8 @@
 import { ComponentFixture, TestBed, waitForAsync } from '@angular/core/testing';
 import { FormsModule } from '@angular/forms';
-import { NgbDatepickerModule } from '@ng-bootstrap/ng-bootstrap';
+import { By } from '@angular/platform-browser';
+import { NgbInputDatepicker, NgbDatepickerModule } from '@ng-bootstrap/ng-bootstrap';
+import { DateFormat } from 'src/web/types/datetime-const';
 import { DatepickerComponent } from './datepicker.component';
 
 describe('DatepickerComponent', () => {
@@ -27,4 +29,21 @@ describe('DatepickerComponent', () => {
   it('should create', () => {
     expect(component).toBeTruthy();
   });
+
+  it('should emit the date for changeDate', () => {
+    const changeDateSpy = jest.spyOn(component.dateChangeCallback, 'emit');
+    const date : DateFormat = { year: 2023, month: 10, day: 12 };
+    component.changeDate(date);
+    expect(changeDateSpy).toHaveBeenCalledWith(date);
+  });
+
+  it('the datepicker should navigate to today\'s date for selectTodayDate', () => {
+    const datepicker = fixture.debugElement.query(By.directive(NgbInputDatepicker)).injector.get(NgbInputDatepicker);
+    const todayDate = component.calendar.getToday();
+    const selectTodayDateSpy = jest.spyOn(component.dateChangeCallback, 'emit');
+    const datePickerNavigateSpy = jest.spyOn(datepicker, 'navigateTo');
+    component.selectTodayDate(datepicker);
+    expect(selectTodayDateSpy).toHaveBeenCalledWith(todayDate);
+    expect(datePickerNavigateSpy).toHaveBeenCalledWith(todayDate);
+  });
 });