express-error-middleware.spec.ts

import type express from 'express';
import request from 'supertest';
import { describe, expect, it } from 'vitest';

import { createApp, createProxyMiddleware } from './test-kit.js';

describe('express error middleware', () => {
  it('should propagate error to express', async () => {
    let httpProxyError: Error | undefined;

    const proxyMiddleware = createProxyMiddleware({
      changeOrigin: true,
      router: (req) => undefined, // Trigger "Error: Must provide a proper URL as target"
    });

    const errorMiddleware: express.ErrorRequestHandler = (err, req, res, next) => {
      httpProxyError = err;
      res.status(504).send('Something broke!');
    };

    const app = createApp(proxyMiddleware, errorMiddleware as any);
    const response = await request(app).get('/get').expect(504);

    expect(httpProxyError?.message).toBe('Must provide a proper URL as target');
    expect(response.text).toBe('Something broke!');
  });
});