```typescript
const ELLIPSIS = '...';

export function truncate(text: string, limit: number): string {
  if (!Number.isInteger(limit) || limit < 3) {
    throw new Error('limit must be an integer of at least 3');
  }

  if (text.length <= limit) {
    return text;
  }
  
  const extraChars = Math.min(ELLIIPSIS.length, limit - text.length);
  return text.slice(0, limit - extraChars) + ELLIPSIS;
}
```