Testing async/await middleware?

We’re looking to migrate over to Koa 2. So far i’ve converted from generators to async await but I’m having a hard time wrapping my head around how to update my unit tests to test context bubbling up. I’ve scoured your code and other repo’s seeing if anyone has good middleware examples but come up short.

I used to test my middleware as such:

const gen = someMiddleware.call(koaContext);
// Here I force bubble up behavior allowing my middleware to add 
// or manipulate data on the context.
gen.next().next();

koaContext.state.someValue.should.equal(...)

How do I accomplish the same bubble up behavior using async await?

[marvinhagemeister]

In the end all a middleware does is mutate the Context. With that in mind testing is as easy as this:

// Custom middleware
const foo = (ctx, next) => {
  ctx.state = {
    bar: "Hello World!",
  };

  await next();
}

// Test case
it("should set bar", async () => {
  const mock = {
    state: undefined,
  };

  // Simply pass a noop function as `next` argument
  const noop = () => { };
  await foo(mock, noop);
  assert.equal(mock.state.bar, "Hello World!");
});

[robinpokorny]

This issue inspired me to give a talk about testing Koa middleware and later I put it into a form of an article: https://medium.com/@robinpokorny/async-testing-koa-with-jest-1b6e84521b71

Maybe someone, who google this problem, will find it interesting.