带有参数的单元测试Mocha Chai

Question

I m building a little library using Nodejs and I m having some troubles unit testing with mocha and chai.

My problem happens when I try to spy on a function, and expect it to have been called with some parametes.

Actually, when I log, the parameters passed to the function are good. But the test is failing again and again.

Here's what I m testing :

import callback from './callback'
/**
 * Connect the express routes with the injector directly inside of the app
 * @param  {Object} app      An express application, or an application that has the same api
 * @param  {Object} injector An injector with the interface of deepin module
 * @param  {Object} parser   An object with the interface of route-parser module
 */
const expressKonnector = (app, injector, parser) => {
  const routes = parser.parseRoutes()
  for (const route of routes) {
    app[route.method](route.pattern, callback(injector, route))
  }
}

export default expressKonnector

Here's the callback dependent module :

import callbackRender from './callbackRender'
import { HttpRequest } from 'default-http'

export default (injector, route) => {
  const ctrl = injector.get(route.controller)
  return (request, response) => {
    const result = ctrl[route.controllerMethod](new HttpRequest())
    if (result.then) {
      return result.then(res => callbackRender(res, response))
    } else {
      callbackRender(result, response)
    }
  }
}

And here's the failing test :

  it('should call the app.get method with pattern /users/:idUser and a callback', () => {
      const spy = chai.spy.on(app, 'get')
      const routes = routeParser.parseRoutes()
      expressKonnector(app, injector, routeParser)
      expect(spy).to.have.been.called.with('/users/:idUser', callback(injector, routes[1]))
    })

I have the following stack when the test fails :

ExpressKonnector  ExpressKonnector should call the app.get method with pattern /users/:idUser and a callback:
AssertionError: expected { Spy, 3 calls } to have been called with [ '/users/:idUser', [Function] ]
at Context.<anonymous> (C:/Project/javascript/express-konnector/src/test/expressKonnector.spec.js:176:43)

If you want to have more detail, or simply run the "npm install && npm test command", you can have the module on this github (dev branch) :

https://github.com/Skahrz/express-konnector

Answer 1

callback() returns a new function every time, so they can't be compared to each other.

To demonstrate:

const giveFunc = () => () => 'bar';

let func1 = giveFunc();
let func2 = giveFunc();
console.log( func1 === func2 ); // false

You can do a partial match instead, to validate the first argument:

expect(spy).to.have.been.called.with('/users/:idUser');

If you really want to test if the right function gets passed, you can't use an anonymous function, so you'll have to name it:

return function callbackFunc(request, response) {
  ...
};

You subsequently have to find the function argument to the spy, and check its name against what's expected:

expect(spy.args[0][1].name).to.equal('callbackFunc');

Where spy.args[0][1] means "the second argument ( [1] ) for the first call ( [0] ) to the spy" , which should be the function generated by callback() .

Since your spy gets called three times, you probably want to iterate over spy.args and check each one for the correct function argument.