feat(cart): implement add to cart functionality and display empty cart message

src/app/shared/components/cart/cart.component.spec.ts

@@ -24,6 +24,44 @@ describe('CartComponent', () => {
     TestBed.resetTestingModule();
   });
 
+  it('shows an empty cart message when there are no items', async () => {
+    await TestBed.configureTestingModule({
+      imports: [CartComponent],
+      providers: [
+        {
+          provide: CartService,
+          useValue: {
+            cart: signal(null).asReadonly(),
+            updateItemQuantity: vi.fn(),
+            removeItem: vi.fn(),
+          },
+        },
+        {
+          provide: ModalService,
+          useValue: {},
+        },
+        {
+          provide: ToastService,
+          useValue: {
+            success: vi.fn(),
+            info: vi.fn(),
+            danger: vi.fn(),
+          },
+        },
+      ],
+    }).compileComponents();
+
+    const fixture = TestBed.createComponent(CartComponent);
+    fixture.detectChanges();
+
+    const emptyMessage = fixture.debugElement.query(By.css('.cart-empty-message'));
+
+    expect(emptyMessage).not.toBeNull();
+    expect(emptyMessage.nativeElement.textContent.trim()).toBe('El carrito está vacío');
+    expect(fixture.debugElement.query(By.css('app-cart-item'))).toBeNull();
+    expect(fixture.debugElement.query(By.css('.cart-footer'))).toBeNull();
+  });
+
   it('opens a confirm delete modal before removing an item', async () => {
     const removeItem = vi.fn().mockReturnValue(of({ message: 'Producto eliminado.' }));
     const openConfirmDelete = vi.fn().mockReturnValue(of(true));
@@ -71,6 +109,8 @@ describe('CartComponent', () => {
     ]);
     fixture.detectChanges();
 
+    expect(fixture.debugElement.query(By.css('.cart-item-media'))).toBeNull();
+
     fixture.debugElement.query(By.css('app-cart-item')).triggerEventHandler('remove');
 
     expect(openConfirmDelete).toHaveBeenCalledWith({