update

test/image-cap.test.js

@@ -0,0 +1,23 @@
+'use strict';
+const assert = require('node:assert');
+const { capImage } = require('../lib/image-cap');
+
+let passed = 0;
+function check(name, fn) {
+  try { fn(); console.log('  ok -', name); passed++; }
+  catch (e) { console.error('  FAIL -', name, e.message); process.exitCode = 1; }
+}
+
+check('small buffer returned untouched', () => {
+  const buf = Buffer.alloc(1024); // 1 KB
+  const r = capImage(buf);
+  assert.strictEqual(r.buf, buf, 'small images should not be modified');
+  assert.strictEqual(r.preview, null);
+});
+
+check('oversized buffer triggers preview placeholder', () => {
+  const buf = Buffer.alloc(3 * 1024 * 1024); // 3 MB
+  const r = capImage(buf);
+  assert.ok(r.preview !== null, 'oversized images should produce preview');
+  assert.strictEqual(r.preview, '[图片]');
+});