From 73d3e4801af42a7784d2c9972cf0daa85be5e21c Mon Sep 17 00:00:00 2001
From: Shreedhar Bhat <shridharbhat1998@gmail.com>
Date: Mon, 21 Apr 2025 10:30:53 +0530
Subject: [PATCH] test(reading-time): Unit tests for calculating reading time

---
 .../src/__tests__/readingTime.test.ts         | 56 +++++++++++++++++++
 .../src/blogUtils.ts                          |  4 +-
 .../src/readingTime.ts                        | 27 +++++++++
 3 files changed, 85 insertions(+), 2 deletions(-)
 create mode 100644 packages/docusaurus-plugin-content-blog/src/__tests__/readingTime.test.ts
 create mode 100644 packages/docusaurus-plugin-content-blog/src/readingTime.ts

diff --git a/packages/docusaurus-plugin-content-blog/src/__tests__/readingTime.test.ts b/packages/docusaurus-plugin-content-blog/src/__tests__/readingTime.test.ts
new file mode 100644
index 0000000000..d48d6dffda
--- /dev/null
+++ b/packages/docusaurus-plugin-content-blog/src/__tests__/readingTime.test.ts
@@ -0,0 +1,56 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {calculateReadingTime} from '../readingTime';
+
+describe('calculateReadingTime', () => {
+  it('calculates reading time for empty content', () => {
+    expect(calculateReadingTime('')).toBe(0);
+  });
+
+  it('calculates reading time for short content', () => {
+    const content = 'This is a short test content.';
+    expect(calculateReadingTime(content)).toBe(0.02);
+  });
+
+  it('calculates reading time for long content', () => {
+    const content = 'This is a test content. '.repeat(100);
+    expect(calculateReadingTime(content)).toBe(1.6666666666666667);
+  });
+
+  it('respects custom words per minute', () => {
+    const content = 'This is a test content. '.repeat(100);
+    expect(calculateReadingTime(content, {wordsPerMinute: 100})).toBe(5);
+  });
+
+  it('handles content with special characters', () => {
+    const content = 'Hello! How are you? This is a test...';
+    expect(calculateReadingTime(content)).toBe(0.02666666666666667);
+  });
+
+  it('handles content with multiple lines', () => {
+    const content = `This is line 1.
+    This is line 2.
+    This is line 3.`;
+    expect(calculateReadingTime(content)).toBe(0.04);
+  });
+
+  it('handles content with HTML tags', () => {
+    const content = '<p>This is a <strong>test</strong> content.</p>';
+    expect(calculateReadingTime(content)).toBe(0.016666666666666666);
+  });
+
+  it('handles content with markdown', () => {
+    const content = '# Title\n\nThis is **bold** and *italic* text.';
+    expect(calculateReadingTime(content)).toBe(0.02666666666666667);
+  });
+
+  it('handles CJK content', () => {
+    const content = '你好，世界！这是一段测试内容。';
+    expect(calculateReadingTime(content)).toBe(0.04);
+  });
+});
diff --git a/packages/docusaurus-plugin-content-blog/src/blogUtils.ts b/packages/docusaurus-plugin-content-blog/src/blogUtils.ts
index ab7426eac5..2cc84bac76 100644
--- a/packages/docusaurus-plugin-content-blog/src/blogUtils.ts
+++ b/packages/docusaurus-plugin-content-blog/src/blogUtils.ts
@@ -9,7 +9,6 @@ import fs from 'fs-extra';
 import path from 'path';
 import _ from 'lodash';
 import logger from '@docusaurus/logger';
-import readingTime from 'reading-time';
 import {
   parseMarkdownFile,
   normalizeUrl,
@@ -32,6 +31,7 @@ import {getTagsFile} from '@docusaurus/utils-validation';
 import {validateBlogPostFrontMatter} from './frontMatter';
 import {getBlogPostAuthors} from './authors';
 import {reportAuthorsProblems} from './authorsProblems';
+import {calculateReadingTime} from './readingTime';
 import type {TagsFile} from '@docusaurus/utils';
 import type {LoadContext, ParseFrontMatter} from '@docusaurus/types';
 import type {
@@ -211,7 +211,7 @@ async function parseBlogPostMarkdownFile({
 }
 
 const defaultReadingTime: ReadingTimeFunction = ({content, options}) =>
-  readingTime(content, options).minutes;
+  calculateReadingTime(content, options);
 
 async function processBlogSourceFile(
   blogSourceRelative: string,
diff --git a/packages/docusaurus-plugin-content-blog/src/readingTime.ts b/packages/docusaurus-plugin-content-blog/src/readingTime.ts
new file mode 100644
index 0000000000..d263a8c6fb
--- /dev/null
+++ b/packages/docusaurus-plugin-content-blog/src/readingTime.ts
@@ -0,0 +1,27 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import readingTime from 'reading-time';
+
+const DEFAULT_WORDS_PER_MINUTE = 300;
+
+interface ReadingTimeOptions {
+  wordsPerMinute?: number;
+  wordBound?: (char: string) => boolean;
+}
+
+/**
+ * Calculates the reading time for a given content string.
+ * Uses the reading-time package under the hood.
+ */
+export function calculateReadingTime(
+  content: string,
+  options: ReadingTimeOptions = {},
+): number {
+  const wordsPerMinute = options.wordsPerMinute ?? DEFAULT_WORDS_PER_MINUTE;
+  return readingTime(content, {wordsPerMinute}).minutes;
+}