如何使用express路由器处理文件上传？

下面是我的服务器端index.js：

import Express from 'express';
import fileUpload from 'express-fileupload';
import http from 'http';
import TestRouter from "./TestRouter.js";
let app = new Express();
let httpServer = http.createServer(app);

app.use(Express.json());
app.use(fileUpload({debug:true}));

app.post('/test/uploadFile',async (req, res, next) => {
    console.log(req.body);
    Object.keys(req.files).forEach(key=>{
        console.log("Name:"+req.files[key].name);
        console.log("MIMETYPE:"+req.files[key].mimetype);
        console.log("File size:"+req.files[key].size);
        console.log("==================================");
    });
    res.status(200).end();
});
let portNo=8080;
httpServer.listen(portNo, () => {
    console.log('Express server is running on localhost:'+portNo);
})

工作正常。当我将代码更改为：

import Express from 'express';
import fileUpload from 'express-fileupload';
import http from 'http';
import TestRouter from "./TestRouter.js";
let app = new Express();
let httpServer = http.createServer(app);

app.use(Express.json());
app.use(fileUpload({debug:true}));
app.use('/test', TestRouter);
let portNo=8080;
httpServer.listen(portNo, () => {
    console.log('Express server is running on localhost:'+portNo);
})

TestRouter.js源代码如下：

import Express from 'express';
let wrapper = function () {
    const router = Express.Router();
    router.post('/:action', async (req, res, next) => {
        console.log(req.params.action);
        switch (req.params.action) {
            case "uploadFile":
                console.log("hi");
                res.status(200).end();
                break
            default:
                next();
                break
        }
    });
    return router;
}
export default wrapper;

我发现TestRouter没有被触发。为什么？