Testing behavior in Koa

app.js

import koa from "koa"
import {behavior1} from "./behavior.js"

var app = koa();

app.use(function* (next) {
  this.body = yield behavior1();
  return yield next;
});

app.listen(3000);

async-request-mock.js

export function asyncRequest () {
    return new Promise((resolve, reject) => {
      process.nextTick(() => {
        resolve('Hello World');
      });
    });
};

behavior-spec.js

import Assert from "assert"
import {behavior1} from "./behavior.js"

describe('behavior', () => {
  describe('behavior1', () => {
    it('returns "Hello World"', function* () {
      let body = yield behavior1();
      Assert.equal(body, 'Hello World');
    });
  });
});

behavior.js

import {asyncRequest} from "./async-request-mock.js"

export function* behavior1 () {
  return yield asyncRequest();
}