test: 为utils/file添加测试用例

- 容量进制转换
- 文件拓展名获取与格式化

tests/unit/utils/file.test.ts

@@ -0,0 +1,36 @@
+import {
+  formatFileSize,
+  getFileExtension,
+  formatFileExtension,
+} from '../../../app/utils/file';
+import { expect, test } from 'vitest';
+
+/**
+ * 单元测试: formatFileSize
+ */
+test('formatFileSize - format bytes correctly', () => {
+  expect(formatFileSize(500)).toBe('500.00 B');
+});
+test('formatFileSize - format kilobytes correctly', () => {
+  expect(formatFileSize(2048)).toBe('2.00 KB');
+});
+test('formatFileSize - format megabytes correctly', () => {
+  expect(formatFileSize(5 * 1024 * 1024)).toBe('5.00 MB');
+});
+
+/**
+ * 单元测试: getFileExtension, formatFileExtension
+ */
+test('getFileExtension - extract extension from filename', () => {
+  expect(getFileExtension('document.pdf')).toBe('pdf');
+});
+test('getFileExtension - handle filenames without extension', () => {
+  expect(getFileExtension('README')).toBe('');
+});
+
+test('formatFileExtension - format extension without dot', () => {
+  expect(formatFileExtension('txt')).toBe('TXT');
+});
+test('formatFileExtension - format extension with dot', () => {
+  expect(formatFileExtension('.jpg')).toBe('JPG');
+});