Add unit tests for utils and module pure functions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/unit/module/sortNumEngZhtw.test.js

@@ -0,0 +1,52 @@
+import { describe, it, expect } from 'vitest';
+import {
+  sortNumEngZhtw,
+  sortNumEngZhtwForFilter,
+} from '@/module/sortNumEngZhtw.js';
+
+describe('sortNumEngZhtw', () => {
+  it('sorts numbers in ascending order', () => {
+    expect(sortNumEngZhtw(['3', '1', '2']))
+      .toEqual(['1', '2', '3']);
+  });
+
+  it('places numbers before strings', () => {
+    expect(sortNumEngZhtw(['b', '1', 'a']))
+      .toEqual(['1', 'a', 'b']);
+  });
+
+  it('sorts English strings alphabetically', () => {
+    expect(sortNumEngZhtw(['cherry', 'apple', 'banana']))
+      .toEqual(['apple', 'banana', 'cherry']);
+  });
+
+  it('sorts mixed numbers and strings', () => {
+    const input = ['banana', '10', 'apple', '2'];
+    const result = sortNumEngZhtw(input);
+    expect(result).toEqual(['2', '10', 'apple', 'banana']);
+  });
+});
+
+describe('sortNumEngZhtwForFilter', () => {
+  it('returns negative when a < b (numbers)', () => {
+    expect(sortNumEngZhtwForFilter('1', '2'))
+      .toBeLessThan(0);
+  });
+
+  it('returns positive when a > b (numbers)', () => {
+    expect(sortNumEngZhtwForFilter('10', '2'))
+      .toBeGreaterThan(0);
+  });
+
+  it('places numbers before strings', () => {
+    expect(sortNumEngZhtwForFilter('1', 'a'))
+      .toBeLessThan(0);
+    expect(sortNumEngZhtwForFilter('a', '1'))
+      .toBeGreaterThan(0);
+  });
+
+  it('compares strings using locale', () => {
+    expect(sortNumEngZhtwForFilter('a', 'b'))
+      .toBeLessThan(0);
+  });
+});