Added cypress tests

app/cypress/e2e/container.spec.js

@@ -0,0 +1,90 @@
+// cypress/e2e/container.spec.js
+
+describe('Custom Scroll & Container Resizing', () => {
+  beforeEach(() => {
+    // Assumes your app is running at baseUrl, and container.js is loaded on “/”
+    cy.visit('/');
+  });
+
+  it('on load, the scroll-container gets a positive height and proper overflow', () => {
+    // wait for our JS to run
+    cy.window().should('have.property', 'adjustScrollContainerHeight');
+
+    // Grab the inline style of .scroll-container
+    cy.get('.scroll-container')
+      .should('have.attr', 'style')
+      .then(style => {
+        // height:<number>px must be present
+        const m = style.match(/height:\s*(\d+(?:\.\d+)?)px/);
+        expect(m, 'height set').to.not.be.null;
+        expect(parseFloat(m[1]), 'height > 0').to.be.greaterThan(0);
+
+        // overflow shorthand should include both hidden & auto (order-insensitive)
+        expect(style).to.include('overflow:');
+        expect(style).to.match(/overflow:\s*(hidden\s+auto|auto\s+hidden)/);
+      });
+  });
+
+  it('on window resize, scroll-container height updates', () => {
+    // record original height
+    cy.get('.scroll-container')
+      .invoke('css', 'height')
+      .then(orig => {
+        // resize to a smaller viewport
+        cy.viewport(320, 480);
+        cy.wait(100); // allow resize handler to fire
+
+        cy.get('.scroll-container')
+          .invoke('css', 'height')
+          .then(newH => {
+            expect(parseFloat(newH), 'height changed on resize').to.not.equal(parseFloat(orig));
+          });
+      });
+  });
+
+  context('custom scrollbar thumb', () => {
+    beforeEach(() => {
+      // inject tall content to force scrolling
+      cy.get('.scroll-container').then($sc => {
+        $sc[0].innerHTML = '<div style="height:2000px">long</div>';
+      });
+      // re-run scrollbar setup
+      cy.window().invoke('updateCustomScrollbar');
+    });
+
+    it('shows a thumb with reasonable size & position', () => {
+      cy.get('#custom-scrollbar').should('have.css', 'opacity', '1');
+
+      cy.get('#scroll-thumb')
+        .should('have.css', 'height')
+        .then(h => {
+          const hh = parseFloat(h);
+          expect(hh).to.be.at.least(20);
+          // ensure thumb is smaller than container
+          cy.get('#custom-scrollbar')
+            .invoke('css', 'height')
+            .then(ch => {
+              expect(hh).to.be.lessThan(parseFloat(ch));
+            });
+        });
+
+      // scroll a bit and verify thumb.top changes
+      cy.get('.scroll-container').scrollTo(0, 200);
+      cy.wait(50);
+      cy.get('#scroll-thumb')
+        .invoke('css', 'top')
+        .then(t => {
+          expect(parseFloat(t)).to.be.greaterThan(0);
+        });
+    });
+
+    it('hides scrollbar when content fits', () => {
+      // remove overflow
+      cy.get('.scroll-container').then($sc => {
+        $sc[0].innerHTML = '<div style="height:10px">tiny</div>';
+      });
+      cy.window().invoke('updateCustomScrollbar');
+      cy.get('#custom-scrollbar').should('have.css', 'opacity', '0');
+    });
+  });
+});