chore: add elastic-sticky.cy.ts (#6666)

projects/demo-cypress/src/tests/elastic-sticky.cy.ts

@@ -0,0 +1,64 @@
+import {Component} from '@angular/core';
+import {TuiElasticStickyModule} from '@taiga-ui/addon-mobile';
+import {TuiRootModule, TuiScrollbarModule} from '@taiga-ui/core';
+
+describe('ElasticSticky', () => {
+    let component: TestComponent;
+
+    @Component({
+        template: `
+            <tui-root>
+                <div
+                    id="scroll"
+                    style="position: relative; height: 100px; overflow: auto"
+                    tuiScrollRef
+                >
+                    <div style="height: 50px">I'm header</div>
+                    <div
+                        style="position: sticky; height: 50px; top: 0"
+                        (tuiElasticSticky)="onElastic($event)"
+                    >
+                        I'm sticky
+                    </div>
+                    <div style="height: 100px">I'm footer</div>
+                </div>
+            </tui-root>
+        `,
+    })
+    class TestComponent {
+        activeItemIndex = 0;
+        offset = NaN;
+
+        onElastic(value: number): void {
+            this.offset = value;
+        }
+    }
+
+    beforeEach(() =>
+        cy
+            .mount(TestComponent, {
+                imports: [TuiRootModule, TuiScrollbarModule, TuiElasticStickyModule],
+            })
+            .then(wrapper => {
+                component = wrapper.component;
+            }),
+    );
+
+    it('callback is not triggered initially', () => {
+        void expect(Number.isNaN(component.offset)).to.true;
+    });
+
+    it('callback is triggered with 0.5 when half of sticky would be hidden', () => {
+        cy.get('#scroll')
+            .then(query => query.get(0).scrollTo({top: 75}))
+            .then(() => cy.wait(100))
+            .then(() => expect(Number(component.offset.toFixed(1))).to.equal(0.5));
+    });
+
+    it('callback is triggered with 0 when sticky is fully hidden', () => {
+        cy.get('#scroll')
+            .then(query => query.get(0).scrollTo({top: 100}))
+            .then(() => cy.wait(100))
+            .then(() => expect(Number(component.offset.toFixed(1))).to.equal(0));
+    });
+});