Rails tests: Net::HTTP post - empty response.body in Rspec when fetching external site

Strange RSpec behaviour: I send a post request from a test.

context "when webmaster" do
    let(:question) { create(:question) }
    let(:user) { create(:user, :webmaster) }

    describe "creating question from admin form" do
      it "not success" do
        sign_in(user)
        region = "1c5b2444-70a0-4932-980c-b4dc0d3f02b5"
        params = { question: {
          phone: 123,
          region: region_id
        }}

        # Same application
        post :create_from_webmaster_modal, params: params
        expect(response).to have_http_status(:ok)
      end
    end
  end

It calls the application controller (same application)

# This controller in the same application
def create_from_webmaster_modal
  ...
    # Fetch external site
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true
    response = http.post(uri.path, params.to_json, headers)

    # When called from RSpec, body is empty
    json_response = JSON.parse(response.body) 
  ...
end

... which fetches data from an external API.
In all cases, code in controller fetches data from external API.

In console (rails c) in all environments (production, development, test) everything works without errors.

In the case of running

RAILS_ENV=test bundle exec rspec

response.body is empty and the response is Net::HTTPOK

All parameters coming into http.post(...) are correct.
<pre>
Rails 5.2
Ruby - 2.5 (yes, it's an old application (( )
Rspec - 3.10
</pre>
Whats happend?

It's difficult to answer this question because we don't know what's happening when that request is being made. You're relying on an external service to be available during any run of your test suite and you're relying on it being consistent in its response. That's a violation of FIRST principles.

You can try to troubleshoot the spec by putting binding.irb inside your controller action:

# This controller in the same application
def create_from_webmaster_modal
  ...
    # Fetch external site
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true
    response = http.post(uri.path, params.to_json, headers)

    binding.irb

    # When called from rspec, body is empty
    json_response = JSON.parse(response.body) 
  ...
end

When you run the test it will open a REPL at that point and you can use it to inspect everything in the scope of that method with the ls command. You should check that all the variables and methods that are used in the request are what you expect them to be, and you can attempt to re-run the response = http.post(uri.path, params.to_json, headers) command in the REPL to ensure that it's making the connection that you expect it to.

One issue is that we don't know what your shell or application environments look like when you run any given shell command. It's possible that the way that you start the Rails console is injecting some environment variables but the way that you start RSpec is not injecting those variables. Make sure that you're starting them consistently and with bundle exec, e.g.:

# Start the console in the test environment to run the request
RAILS_ENV=test bundle exec rails console

# And start rspec in the test environment to run the request
RAILS_ENV=test bundle exec rspec

You should also check your spec_helper.rb and rails_helper.rb to ensure that your expected configuration isn't being overwritten.

But all of this is besides the point: you shouldn't be testing the availability or response status of an external service during your unit tests. Test your code, not external services. For something like this you should be using a gem like VCR to record and replay remote requests so that your specs are always repeatable and consistent and fast. Alternatively, you can just mock it.

Disclaimer : I don't have enough reputation to comment, this post should ideally be a comment

I tested on a brand new rails app, adding HTTParty and requesting the same url you do in your env : the body is not empty

I think the problem is not in httparty

Do you happen to have any initializer or library in your Rails env that might disable net connect only for test environment ?
Something such as webmock or so ? Here's webmock usage and how it returns empty body

Maybe at the "spec_helper.rb" level that way you only see the problem in your test suite ?

This could explain any URL fetch to return http success code as well as empty body

Can you try an invalid URL in your HTTParty.get?

such as HTTParty.get('https://invalidexample.com/').body
If you still have a 200 OK and empty body you have a lib somewhere tampering with external requests only on TEST ENV

(as pointed in other answers this should be the best way to test your code anyway, no real connection)