spicy-chai.js

// http client
const chai = require('chai');
const chaiHttp = require('chai-http');
chai.use(chaiHttp);
const should = chai.should();

/*
* chai enhanced request factory
*
* Allows to transform requests before sending. Add transformer functions by
* calling `addRequestTransformer` and passing a function that mutates request.
*
* You can add more than one request transformer.
*
* Requires: ES5
*
* Usage:
*
*  const client = spicyChai('http://example.com');
*  const credentials = {
*      'username': 'user@example.com',
*      'password': 'password1234'
*  };
*
*  client.post('/account/login')
*        .send(credentials)
*        .end((err, res) => {
*          const authToken = res.body['access_token'];
*          client.addRequestTransformer((req) => {
*              req.set('Authorization', `Bearer ${authToken}`);
*          });
*   });
*
**/
function spicyChai(baseUrl) {
    const __requestTransformers = [];
    // kudos to Dr. Axel Rauschmayer
    // http://exploringjs.com/es6/ch_proxies.html#_intercepting-method-calls
    const handler = {
        get(target, propKey, receiver) {
            // intercept call to addRequestTransformer()
            if (propKey === 'addRequestTransformer') {
                return function(...args) {
                    __requestTransformers.push(...args);
                };
            }
            // intercept other calls
            const origMethod = target[propKey];
            return function(...args) {
                let result = origMethod.apply(this, args);
                // chain through transformers
                for (const runTransformerFn of __requestTransformers) {
                    const newResult = runTransformerFn(result);
                    // don't rewrite request with undefined if
                    // transformer didn't return anything
                    if (newResult) {
                        result = newResult;
                    }
                }
                return result;
            };
        }
    };
    return new Proxy(chai.request(baseUrl), handler);
}

/*
 *   Example usage with test assertions
 */

const apiUrl = 'http://api.example.com';
const client = spicyChai(apiUrl); // equivalent of chai.request(apiUrl)

describe('Test Login Operations', function() {
    describe('Login', () => {
        it('should login as dave', (done) => {
            client.post('/account/login').send({
                'username': 'user@example.com',
                'password': 'password1234'
            }).end((err, res) => {
                should.not.exist(err);
                const authToken = res.body['access_token'];
                client.addRequestTransformer((req) => {
                    req.set('Authorization', `Bearer ${authToken}`);
                });
                done();
            });
        });
        it('should get a profile', (done) => {
            client.get('/account/profile').end((err, res) => {
                should.not.exist(err);
                done();
            });
        });
    });
});