Rspec request specs and Rails 5 - ruby-on-rails

Question

I'm starting a new project, my first with Rails 5.1.0. I have a pb with my first request spec.
describe 'Users', type: :request do
it 'are created from external data' do
json_string = File.read('path/to/test_data/user_data.json')
params = { user: JSON.parse(json_string) }
headers = { "CONTENT_TYPE" => "application/json" }
expect do
post '/api/v1/users', params.to_s, headers
end.to change {
User.count
}.by(1)
expect(response.status).to eq 200
end
end
this spec return the error ArgumentError: wrong number of arguments (given 3, expected 1). The official documentation don't say much.
If I take out the .to_s, and send a hash, like this:
post '/api/v1/users', params, headers
I got another error:
ArgumentError: unknown keyword: user
Any thought?

Answer 1

I think they changed the syntax recently. Now it should use keyword args. So, something like this:
post '/api/v1/users', params: params, headers: headers

Answer 2

Here's a little addendum to Sergio's answer. If you are upgrading from Rails 4 to Rails 5, have lots of tests, and aren't too keen on changing them all – at least not until you've finished upgrading – I've found a way to make them work with the old method signature.
In my spec_helper I added
module FixLegacyTestRequests
def get(path, par = {}, hdr = {})
process(:get, path, params: par, headers: hdr)
end
def post(path, par = {}, hdr = {})
process(:post, path, params: par, headers: hdr)
end
def put(path, par = {}, hdr = {})
process(:put, path, params: par, headers: hdr)
end
def delete(path, par = {}, hdr = {})
process(:delete, path, params: par, headers: hdr)
end
end
and then I added this configuration for each test:
RSpec.configure do |config|
config.before :each do |example|
extend(FixLegacyTestRequests) # to be removed at some point!
end
end
My tests went back to working, and I think it should be safe because it's only applied to the currently running test and shouldn't pollute any gem's code such as with a monkey patch.