koa-unit.js

// BAD APPROACH
const heartbeat = require('./heartbeat'),
    coTape = require('co-tape'),
    tape = require('tape');
    
tape('heartbeat', function(t) {
  t.test('serves heartbeat request', coTape(function*(t) {
    t.plan(1);
    
    // add some knowledge of implementation details of what we're testing
    let koaContext = {
      path: '/heartbeat'
    },
      next = function(cb) { cb(); };
    
    yield heartbeat.apply(koaContext, next);
    
    t.equal(koaContext.body, 'OK', 'returns the correct response');
  }));
});