单元测试表达路由器

Question

I know this has been discussed a couple of times. Anyway, I feel like all the provided solutions don't (perfectly) fit to my requirement(s). I have the following code:

router.js:
------------------
var Router = function(app, resourceName, controller) {
    //Create
    app.post('/api/' + resourceName, function(req, res) {
        console.log('Incoming request: ' + resourceName + ' (POST)');
        controller.create(req, res);
    });
};

module.exports = Router;

As you can see this is a very "generic" router. It can be instantiated for example in the server like this:

var app = express();
var userController = ...
var userRouter = new Router(app, 'Users', userController);

So I don't have to write a file per resource but I just have one generic router.

I would like to test my generic router but I see some problems:

1. How to "inject" the app? I could create an instance of Express ( var app = express(); ) but I think a mock would be better (as this is a unit test, not an integration test!). What's the best way to get an appropriate mock?
2. What exactly should I test? As far as I see my router itself (without integration) isn't doing anything else but console output (not worth to test) and a call of a function ( controller.create(req, res); ). How should I test if this function is called? Or is there anything else to test?

Answer 1

1. You should probably make a stub implementation of app.

2. What you want to test is that the constructor registers listeners on specified routes + HTTP methods. I would advise putting Sinon.js stubs into your app stub, and then in your tests check that they are called with expected arguments.

Answer 2

1. I would use jasmine.createSpyObj to mock app (and maybe controller as well).
2. I think you just need to test that app.post gets called with the arguments '/api/' + resourceName and controller.create, because you aren't testing that express.post works correctly or not.

Here's how I'd do those two things specifically.

I'd modify router.js a little bit to make this easier:

var Router = function(app, resourceName, controller) {
  app.post('/api/' + resourceName, controller.create.bind(controller))
}

module.exports = Router;

And then the test would look like this:

describe("Router", function() {
  it("should route /api to controller.create", function() {
    router = require('./router');
    app = jasmine.createSpyObj('application', ['post']);
    controller = jasmine.createSpyObj('controller', ['create']);
    router(app, 'foo', controller);
    expect(app.post).toHaveBeenCalledWith('/api/foo', jasmine.any(Function));
  });
});

This isn't a perfect test because it isn't actually checking that controller.create specifically is getting called. That gets a little more complicated because of the .bind() stuff.

describe("Router", function() {
  it("should route /api to controller.create", function() {
    router = require('./router');
    app = jasmine.createSpyObj('application', ['post']);
    controller = jasmine.createSpyObj('controller', ['create']);
    controller.create = jasmine.createSpyObj('binder', ['bind']);
    controller.create.bind.and.returnValue('bar');
    router(app, 'foo', controller);
    expect(controller.create.bind).toHaveBeenCalledWith(controller);
    expect(app.post).toHaveBeenCalledWith('/api/foo', controller.create.bind(controller));
  });
});