Add test

cypress/e2e/theme-switch.cy.ts

@@ -0,0 +1,35 @@
+describe('ThemeSwitch Component', () => {
+    beforeEach(() => {
+      cy.visit('http://localhost:4321');
+    });
+
+    it('should display the theme switch', () => {
+      cy.get('.switch').should('exist');
+      cy.get('.switch input').should('have.attr', 'type', 'checkbox');
+    });
+
+    it('should toggle dark mode when the switch is clicked', () => {
+      cy.get('html').should('not.have.class', 'dark');
+      cy.get('.switch input').check({ force: true }).should(() => {
+        expect(localStorage.getItem('darkMode')).to.eq('true');
+      });
+      cy.get('html').should('have.class', 'dark');
+
+      cy.get('.switch input').uncheck({ force: true }).should(() => {
+        expect(localStorage.getItem('darkMode')).to.eq('false');
+      });
+      cy.get('html').should('not.have.class', 'dark');
+    });
+
+    it('should retain the theme preference after page reload', () => {
+      cy.get('.switch input').check({ force: true });
+      cy.reload();
+      cy.get('html').should('have.class', 'dark');
+      cy.get('.switch input').should('be.checked');
+
+      cy.get('.switch input').uncheck({ force: true });
+      cy.reload();
+      cy.get('html').should('not.have.class', 'dark');
+      cy.get('.switch input').should('not.be.checked');
+    });
+  });