From bcce235841366fe19a2d301377777192e383523a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rub=C3=A9n=20Norte?= <rubennorte@meta.com>
Date: Wed, 26 Mar 2025 11:09:42 -0700
Subject: [PATCH] Add basic tests for Event Timing API (#50289)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/50289

Changelog: [internal]

Adding basic Fantom tests for the new Event Timing API.

Reviewed By: huntie

Differential Revision: D71734778

fbshipit-source-id: b5da3162fade64eadede72346af50df68b4facd9
---
 .../__tests__/EventTimingAPI-itest.js         | 192 ++++++++++++++++++
 1 file changed, 192 insertions(+)
 create mode 100644 packages/react-native/src/private/webapis/performance/__tests__/EventTimingAPI-itest.js

diff --git a/packages/react-native/src/private/webapis/performance/__tests__/EventTimingAPI-itest.js b/packages/react-native/src/private/webapis/performance/__tests__/EventTimingAPI-itest.js
new file mode 100644
index 00000000000..80684afa3b6
--- /dev/null
+++ b/packages/react-native/src/private/webapis/performance/__tests__/EventTimingAPI-itest.js
@@ -0,0 +1,192 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ * @fantom_flags enableReportEventPaintTime:true
+ */
+
+import 'react-native/Libraries/Core/InitializeCore';
+
+import type {PerformanceObserverEntryList} from 'react-native/src/private/webapis/performance/PerformanceObserver';
+
+import * as Fantom from '@react-native/fantom';
+import nullthrows from 'nullthrows';
+import {useState} from 'react';
+import {Text, View} from 'react-native';
+import setUpPerformanceObserver from 'react-native/src/private/setup/setUpPerformanceObserver';
+import {PerformanceEventTiming} from 'react-native/src/private/webapis/performance/EventTiming';
+import {PerformanceObserver} from 'react-native/src/private/webapis/performance/PerformanceObserver';
+
+setUpPerformanceObserver();
+
+function sleep(ms: number) {
+  const end = performance.now() + ms;
+  while (performance.now() < end) {}
+}
+
+function ensurePerformanceEventTiming(value: mixed): PerformanceEventTiming {
+  if (!(value instanceof PerformanceEventTiming)) {
+    throw new Error(
+      `Expected instance of PerformanceEventTiming but got ${String(value)}`,
+    );
+  }
+
+  return value;
+}
+
+describe('Event Timing API', () => {
+  it('reports events without event handlers or updates', () => {
+    const callback = jest.fn();
+
+    const observer = new PerformanceObserver(callback);
+    observer.observe({entryTypes: ['event']});
+
+    const root = Fantom.createRoot();
+    Fantom.runTask(() => {
+      root.render(<View />);
+    });
+
+    const element = nullthrows(root.document.documentElement.firstElementChild);
+
+    expect(callback).not.toHaveBeenCalled();
+
+    Fantom.dispatchNativeEvent(element, 'click');
+
+    expect(callback).toHaveBeenCalledTimes(1);
+
+    const entryList = callback.mock.lastCall[0] as PerformanceObserverEntryList;
+    const entries = entryList.getEntries();
+
+    expect(entries.length).toBe(1);
+
+    const entry = ensurePerformanceEventTiming(entries[0]);
+
+    expect(entry.entryType).toBe('event');
+    expect(entry.name).toBe('click');
+
+    expect(entry.startTime).toBeGreaterThanOrEqual(0);
+    expect(entry.processingStart).toBeGreaterThan(entry.startTime);
+    expect(entry.processingEnd).toBeGreaterThanOrEqual(entry.processingStart);
+
+    expect(entry.duration).toBeGreaterThanOrEqual(0);
+    expect(entry.duration).toBeGreaterThan(
+      entry.processingEnd - entry.startTime,
+    );
+
+    expect(entry.interactionId).toBeGreaterThanOrEqual(0);
+  });
+
+  it('reports events with handlers but no updates', () => {
+    const callback = jest.fn();
+
+    const observer = new PerformanceObserver(callback);
+    observer.observe({entryTypes: ['event']});
+
+    const SIMULATED_PROCESSING_DELAY = 50;
+
+    const root = Fantom.createRoot();
+    Fantom.runTask(() => {
+      root.render(
+        <View
+          onClick={event => {
+            sleep(SIMULATED_PROCESSING_DELAY);
+          }}
+        />,
+      );
+    });
+
+    const element = nullthrows(root.document.documentElement.firstElementChild);
+
+    expect(callback).not.toHaveBeenCalled();
+
+    Fantom.dispatchNativeEvent(element, 'click');
+
+    expect(callback).toHaveBeenCalledTimes(1);
+
+    const entryList = callback.mock.lastCall[0] as PerformanceObserverEntryList;
+    const entries = entryList.getEntries();
+
+    expect(entries.length).toBe(1);
+
+    const entry = ensurePerformanceEventTiming(entries[0]);
+
+    expect(entry.entryType).toBe('event');
+    expect(entry.name).toBe('click');
+
+    expect(entry.startTime).toBeGreaterThanOrEqual(0);
+    expect(entry.processingStart).toBeGreaterThan(entry.startTime);
+    expect(entry.processingEnd).toBeGreaterThanOrEqual(entry.processingStart);
+
+    expect(entry.processingEnd - entry.processingStart).toBeGreaterThanOrEqual(
+      SIMULATED_PROCESSING_DELAY,
+    );
+
+    expect(entry.duration).toBeGreaterThanOrEqual(0);
+    expect(entry.duration).toBeGreaterThan(
+      entry.processingEnd - entry.startTime,
+    );
+
+    expect(entry.interactionId).toBeGreaterThanOrEqual(0);
+  });
+
+  it('reports events with updates', () => {
+    const callback = jest.fn();
+
+    const observer = new PerformanceObserver(callback);
+    observer.observe({entryTypes: ['event']});
+
+    function MyComponent() {
+      const [count, setCount] = useState(0);
+
+      return (
+        <View
+          onClick={event => {
+            setCount(count + 1);
+          }}>
+          <Text>{count}</Text>
+        </View>
+      );
+    }
+
+    const root = Fantom.createRoot();
+    Fantom.runTask(() => {
+      root.render(<MyComponent />);
+    });
+
+    const element = nullthrows(root.document.documentElement.firstElementChild);
+
+    expect(callback).not.toHaveBeenCalled();
+
+    Fantom.dispatchNativeEvent(element, 'click');
+
+    expect(callback).toHaveBeenCalledTimes(1);
+
+    const entryList = callback.mock.lastCall[0] as PerformanceObserverEntryList;
+    const entries = entryList.getEntries();
+
+    expect(entries.length).toBe(1);
+
+    const entry = ensurePerformanceEventTiming(entries[0]);
+
+    expect(entry.entryType).toBe('event');
+    expect(entry.name).toBe('click');
+
+    expect(entry.startTime).toBeGreaterThanOrEqual(0);
+    expect(entry.processingStart).toBeGreaterThan(entry.startTime);
+    expect(entry.processingEnd).toBeGreaterThanOrEqual(entry.processingStart);
+
+    expect(entry.duration).toBeGreaterThanOrEqual(0);
+    expect(entry.duration).toBeGreaterThan(
+      entry.processingEnd - entry.startTime,
+    );
+
+    // TODO: When Fantom provides structured data from mounting manager, add timestamp to operations and verify that the duration includes that.
+
+    expect(entry.interactionId).toBeGreaterThanOrEqual(0);
+  });
+});