Are our tests reliable?

We use supertest to run our tests in this module. While that tool does a great job, I'm not sure if we're making reliable tests, since Supertest also handles the body according to the `content-type`, which makes me question whether we're doing good tests or if in the future the tests will stop being reliable as we update that dependency.

Ref: https://github.com/ladjs/superagent/pull/1812

cc: @Phillip9587, @jonchurch, @wesleytodd, @UlisesGascon