From be2bb51c70a6885cd6607f0ea5df35f053645817 Mon Sep 17 00:00:00 2001
From: Nick Gerleman <ngerlem@meta.com>
Date: Tue, 15 Aug 2023 21:56:25 -0700
Subject: [PATCH] ListMetricAggregator UTs - cell offset APIs (#38732)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/38732

Unit tests for cell offset APIs. Mostly the same as previous UTs for VirtualizedList a layer higher.

Changelog: [Internal]

Reviewed By: rozele

Differential Revision: D47978633

fbshipit-source-id: 8cb8a2e8125bc7370eabf9f01a3f7529043171c2
---
 .../__tests__/ListMetricsAggregator-test.js   | 144 ++++++++++++++++++
 1 file changed, 144 insertions(+)

diff --git a/packages/virtualized-lists/Lists/__tests__/ListMetricsAggregator-test.js b/packages/virtualized-lists/Lists/__tests__/ListMetricsAggregator-test.js
index ef253fb94636e6..8b22cb18649bca 100644
--- a/packages/virtualized-lists/Lists/__tests__/ListMetricsAggregator-test.js
+++ b/packages/virtualized-lists/Lists/__tests__/ListMetricsAggregator-test.js
@@ -894,4 +894,148 @@ describe('ListMetricsAggregator', () => {
       isMounted: false,
     });
   });
+
+  it('resolves integral offset of already measured cell', () => {
+    const listMetrics = new ListMetricsAggregator();
+    const orientation = {horizontal: false, rtl: false};
+    const props: CellMetricProps = {
+      data: [1, 2, 3, 4, 5],
+      getItemCount: () => nullthrows(props.data).length,
+      getItem: (i: number) => nullthrows(props.data)[i],
+    };
+
+    listMetrics.notifyCellLayout({
+      cellIndex: 0,
+      cellKey: '0',
+      orientation,
+      layout: {
+        height: 10,
+        width: 5,
+        x: 0,
+        y: 0,
+      },
+    });
+
+    listMetrics.notifyCellLayout({
+      cellIndex: 1,
+      cellKey: '1',
+      orientation,
+      layout: {
+        height: 20,
+        width: 5,
+        x: 0,
+        y: 10,
+      },
+    });
+
+    expect(listMetrics.getCellOffsetApprox(1, props)).toEqual(10);
+  });
+
+  it('estimates integral offset of unmeasured cell', () => {
+    const listMetrics = new ListMetricsAggregator();
+    const orientation = {horizontal: false, rtl: false};
+    const props: CellMetricProps = {
+      data: [1, 2, 3, 4, 5],
+      getItemCount: () => nullthrows(props.data).length,
+      getItem: (i: number) => nullthrows(props.data)[i],
+    };
+
+    listMetrics.notifyCellLayout({
+      cellIndex: 0,
+      cellKey: '0',
+      orientation,
+      layout: {
+        height: 10,
+        width: 5,
+        x: 0,
+        y: 0,
+      },
+    });
+
+    listMetrics.notifyCellLayout({
+      cellIndex: 1,
+      cellKey: '1',
+      orientation,
+      layout: {
+        height: 20,
+        width: 5,
+        x: 0,
+        y: 10,
+      },
+    });
+
+    expect(listMetrics.getCellOffsetApprox(2, props)).toEqual(30);
+  });
+
+  it('resolves fractional offset of already measured cell', () => {
+    const listMetrics = new ListMetricsAggregator();
+    const orientation = {horizontal: false, rtl: false};
+    const props: CellMetricProps = {
+      data: [1, 2, 3, 4, 5],
+      getItemCount: () => nullthrows(props.data).length,
+      getItem: (i: number) => nullthrows(props.data)[i],
+    };
+
+    listMetrics.notifyCellLayout({
+      cellIndex: 0,
+      cellKey: '0',
+      orientation,
+      layout: {
+        height: 10,
+        width: 5,
+        x: 0,
+        y: 0,
+      },
+    });
+
+    listMetrics.notifyCellLayout({
+      cellIndex: 1,
+      cellKey: '1',
+      orientation,
+      layout: {
+        height: 20,
+        width: 5,
+        x: 0,
+        y: 10,
+      },
+    });
+
+    expect(listMetrics.getCellOffsetApprox(1.5, props)).toEqual(20);
+  });
+
+  it('estimates fractional offset of unmeasured cell', () => {
+    const listMetrics = new ListMetricsAggregator();
+    const orientation = {horizontal: false, rtl: false};
+    const props: CellMetricProps = {
+      data: [1, 2, 3, 4, 5],
+      getItemCount: () => nullthrows(props.data).length,
+      getItem: (i: number) => nullthrows(props.data)[i],
+    };
+
+    listMetrics.notifyCellLayout({
+      cellIndex: 0,
+      cellKey: '0',
+      orientation,
+      layout: {
+        height: 10,
+        width: 5,
+        x: 0,
+        y: 0,
+      },
+    });
+
+    listMetrics.notifyCellLayout({
+      cellIndex: 1,
+      cellKey: '1',
+      orientation,
+      layout: {
+        height: 20,
+        width: 5,
+        x: 0,
+        y: 10,
+      },
+    });
+
+    expect(listMetrics.getCellOffsetApprox(2.5, props)).toEqual(37.5);
+  });
 });