✨ feature: Implement Gmail message fetching and Excel sheet name truncation

tests/excel.test.ts

@@ -0,0 +1,39 @@
+import { mkdtemp, rm } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import XLSX from 'xlsx';
+import { ExcelWriter } from '../src/output/excel.js';
+
+let dir = '';
+
+beforeEach(async () => {
+  dir = await mkdtemp(join(tmpdir(), 'nlc-excel-'));
+});
+
+afterEach(async () => {
+  await rm(dir, { force: true, recursive: true });
+});
+
+describe('ExcelWriter', () => {
+  it('truncates newsletter sheet names to the Excel 31-character limit', async () => {
+    const path = join(dir, 'catalog.xlsx');
+    const newsletter = 'A Very Long Newsletter Name That Exceeds The Excel Limit';
+
+    await new ExcelWriter(path).write({
+      rows: [
+        {
+          'Source Newsletter': newsletter,
+          Title: 'Post',
+          'Link URL': 'https://example.com'
+        }
+      ],
+      sponsors: [],
+      deadLinks: []
+    });
+
+    const workbook = XLSX.readFile(path);
+    expect(workbook.SheetNames[0]).toBe('A Very Long Newsletter Name Tha');
+    expect(workbook.SheetNames[0].length).toBe(31);
+  });
+});