rails api: send curl in controller test - ruby-on-rails

Question

I'm building a Rails API, and I'm writing a test that sending a curl request works. This seems to be a testing issue, because an actual curl request works:
$ curl -X POST -d temperature=68 localhost:3000/temperature_readings.json
# => {"status":200}
Here's the controller method:
def create
TemperatureReading.create(temperature: params[:temperature])
render json: { status: 200 }
end
Here's the test:
context 'works via a curl request' do
it 'works' do
system "curl -X POST -d 'temperature=68' #{temperature_readings_url(format: 'json')}"
expect(TemperatureReading.last.temperature).to eq(68)
end
end
I'm getting an error from curl that test.host does not resolve:
curl: (6) Could not resolve host: test.host
That makes sense, because when I call temperature_readings_url(format: 'json') from within pry in that method, I get http://test.host/temperatures.json.
Is there a better way to test that my controller can successfully handle a curl request and create the correct record with the correct attributes?
What I've Tried
I made sure that protect_from_forgery with: :null_session is set in ApplicationController so that it doesn't fail with an exception when it can't find the token
I tried adding -H 'Content-Type:application/json' to the curl request to make sure it's hitting the json format in the controller. But it really seems to boil down to the fact that the working URL in the testing environment is test.host.
So I explicitly set request.host to localhost:3000 in the test, which felt a little hacky. But then of course it just posted to my dev database and not my test database, so the test still failed.

Answer 1

Your app doesn't know its host outside the request context, so you have to provide it anyway. This is also hacky:
temperature_readings_url(format: 'json', host: 'localhost:3000').
But you can define it globally in config/enviroments/test.rb:
Rails.application.routes.default_url_options[:host] = 'localhost:3000'
so in test enviroment all url helpers will return localhost:3000 as host by default.