add test

src/components/__tests__/BackToTop.test.js

@@ -0,0 +1,108 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { mount } from '@vue/test-utils';
+import { nextTick } from 'vue';
+
+vi.mock('@/components/ui/tooltip', () => ({
+    Tooltip: { template: '<div><slot /></div>' },
+    TooltipTrigger: { template: '<div><slot /></div>' },
+    TooltipContent: { template: '<div><slot /></div>' }
+}));
+
+vi.mock('@/components/ui/button', () => ({
+    Button: {
+        emits: ['click'],
+        template: '<button data-testid="back-btn" @click="$emit(\'click\', $event)"><slot /></button>'
+    }
+}));
+
+vi.mock('lucide-vue-next', () => ({
+    ArrowUp: { template: '<i />' }
+}));
+
+import BackToTop from '../BackToTop.vue';
+
+function setScrollY(value) {
+    Object.defineProperty(window, 'scrollY', {
+        configurable: true,
+        value
+    });
+}
+
+describe('BackToTop.vue', () => {
+    beforeEach(() => {
+        setScrollY(0);
+        vi.spyOn(window, 'scrollTo').mockImplementation(() => {});
+    });
+
+    afterEach(() => {
+        vi.restoreAllMocks();
+    });
+
+    it('shows button after scroll threshold and scrolls window to top', async () => {
+        const wrapper = mount(BackToTop, {
+            props: {
+                visibilityHeight: 100,
+                teleport: false,
+                tooltip: false
+            }
+        });
+
+        expect(wrapper.find('[data-testid="back-btn"]').exists()).toBe(false);
+
+        setScrollY(120);
+        window.dispatchEvent(new Event('scroll'));
+        await nextTick();
+
+        const btn = wrapper.find('[data-testid="back-btn"]');
+        expect(btn.exists()).toBe(true);
+
+        await btn.trigger('click');
+
+        expect(window.scrollTo).toHaveBeenCalledWith({ top: 0, behavior: 'smooth' });
+    });
+
+    it('uses virtualizer scrollToIndex when provided', async () => {
+        const scrollToIndex = vi.fn();
+        const wrapper = mount(BackToTop, {
+            props: {
+                visibilityHeight: 0,
+                teleport: false,
+                tooltip: false,
+                virtualizer: { scrollToIndex }
+            }
+        });
+
+        window.dispatchEvent(new Event('scroll'));
+        await nextTick();
+
+        const btn = wrapper.get('[data-testid="back-btn"]');
+        await btn.trigger('click');
+
+        expect(scrollToIndex).toHaveBeenCalledWith(0, { align: 'start', behavior: 'auto' });
+        expect(window.scrollTo).not.toHaveBeenCalled();
+    });
+
+    it('scrolls target element to top with auto behavior', async () => {
+        const target = document.createElement('div');
+        target.scrollTop = 200;
+        target.scrollTo = vi.fn();
+
+        const wrapper = mount(BackToTop, {
+            props: {
+                target,
+                behavior: 'auto',
+                visibilityHeight: 100,
+                teleport: false,
+                tooltip: false
+            }
+        });
+
+        target.dispatchEvent(new Event('scroll'));
+        await nextTick();
+
+        const btn = wrapper.get('[data-testid="back-btn"]');
+        await btn.trigger('click');
+
+        expect(target.scrollTo).toHaveBeenCalledWith({ top: 0, behavior: 'auto' });
+    });
+});