ATLAS-5350: Atlas UI: Enhance Purge Audit Results UI

Author: Brijesh619

dashboard/src/hooks/__tests__/useVirtualization.test.ts

@@ -0,0 +1,89 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { renderHook } from '@testing-library/react';
+import { useVirtualization } from '../useVirtualization';
+
+describe('useVirtualization', () => {
+  it('should return empty values when items array is empty', () => {
+    const { result } = renderHook(() =>
+      useVirtualization({ items: [], scrollTop: 0 })
+    );
+
+    expect(result.current).toEqual({
+      visibleItems: [],
+      paddingTop: 0,
+      paddingBottom: 0,
+      startIndex: 0,
+    });
+  });
+
+  it('should calculate visible items and padding correctly for initial state', () => {
+    const items = Array.from({ length: 100 }, (_, i) => i);
+    const { result } = renderHook(() =>
+      useVirtualization({ items, scrollTop: 0, itemHeight: 37, overscan: 10, visibleCount: 40 })
+    );
+
+    // Initial state (scrollTop = 0)
+    // startIndex = max(0, 0 - 10) = 0
+    // endIndex = min(99, 0 + 40 + 10) = 50
+    // visibleItems = items.slice(0, 51)
+
+    expect(result.current.startIndex).toBe(0);
+    expect(result.current.visibleItems.length).toBe(51);
+    expect(result.current.paddingTop).toBe(0);
+
+    // paddingBottom = (100 - 1 - 50) * 37 = 49 * 37 = 1813
+    expect(result.current.paddingBottom).toBe(1813);
+  });
+
+  it('should calculate visible items correctly when scrolled down', () => {
+    const items = Array.from({ length: 100 }, (_, i) => i);
+    // Scrolled 20 items down: 20 * 37 = 740
+    const { result } = renderHook(() =>
+      useVirtualization({ items, scrollTop: 740, itemHeight: 37, overscan: 10, visibleCount: 40 })
+    );
+
+    // startIndex = max(0, 20 - 10) = 10
+    // endIndex = min(99, 20 + 40 + 10) = 70
+
+    expect(result.current.startIndex).toBe(10);
+    expect(result.current.visibleItems.length).toBe(61); // 70 - 10 + 1
+
+    // paddingTop = 10 * 37 = 370
+    expect(result.current.paddingTop).toBe(370);
+
+    // paddingBottom = (100 - 1 - 70) * 37 = 29 * 37 = 1073
+    expect(result.current.paddingBottom).toBe(1073);
+  });
+
+  it('should cap end index at total items length', () => {
+    const items = Array.from({ length: 50 }, (_, i) => i);
+    // Scrolled way past the bottom
+    const { result } = renderHook(() =>
+      useVirtualization({ items, scrollTop: 5000, itemHeight: 37, overscan: 10, visibleCount: 40 })
+    );
+
+    // startIndex = max(0, 135 - 10) = 125
+    // endIndex = min(49, 135 + 40 + 10) = 49
+    // Wait, if startIndex > endIndex, slice will return empty array
+
+    expect(result.current.startIndex).toBe(125);
+    expect(result.current.visibleItems.length).toBe(0);
+    expect(result.current.paddingBottom).toBe(0);
+  });
+});