Why is ruby rails to_json returning string instead of hash?

Question

I am following a tutorial of building a JSON api using ruby version 2.3.1 and rails version 5.0.7. The tutorial is located at https://scotch.io/tutorials/build-a-restful-json-api-with-rails-5-part-two When running RSpec tests, I get:

Failures:

1) AuthenticationController POST /auth/login when request is valid returns an authentication token Failure/Error: before { post 'auth/login', params: valid_credentials, headers: headers }

 NoMethodError:
   undefined method `symbolize_keys' for "{\"email\":\"foo@bar.com\",\"password\":\"foobar\"}":String
 # ./spec/controllers/authentication_controller_spec.rb:32:in `block (4 levels) in <top (required)>'
 # ./spec/rails_helper.rb:85:in `block (3 levels) in <top (required)>'
 # ./spec/rails_helper.rb:84:in `block (2 levels) in <top (required)>'

2) AuthenticationController POST /auth/login When request is invalid returns a failure message Failure/Error: before { post '/auth/login', params: invalid_credentials, headers: headers }

 NoMethodError:
   undefined method `symbolize_keys' for #<String:0x007fcb133e88f8>
 # ./spec/controllers/authentication_controller_spec.rb:41:in `block (4 levels) in <top (required)>'
 # ./spec/rails_helper.rb:85:in `block (3 levels) in <top (required)>'
 # ./spec/rails_helper.rb:84:in `block (2 levels) in <top (required)>'

The AuthenticationControllerSpec to which it refers to is as follows:

    require 'rails_helper'
    RSpec.describe AuthenticationController, type: :controller do
      # Authentication test suite
      describe 'POST /auth/login' do
        # create test user
        let!(:user) { create(:user) }

        # set headers for authorization
        let(:headers) { valid_headers.except('Authorization')  }

        # set test valid and invalid credentials
        let(:valid_credentials) do
           { 
              email: user.email, 
              password: user.password 
           }.to_json 
        end # let(:valid_credentials) do 

        let(:invalid_credentials) do 
          {
             email: Faker::Internet.email,
             password: Faker::Internet.password
          }.to_json
        end # let(:invalid_credentials) do 

        # set request.headers to our custom headers
        # before { allow(request).to receive(:headers).and_return(headers) }

        # returns auth token when request is valid
        context 'when request is valid' do
          before { post 'auth/login', params: valid_credentials, headers: headers }

          it 'returns an authentication token' do
            expect(json['auth_token']).not_to be_nil
          end #  it 'returns an authentication token' do
end #     context 'when request is valid' do

        # returns failure message when request is invalid
        context 'When request is invalid' do
          before { post '/auth/login', params: invalid_credentials, headers: headers }

          it 'returns a failure message' do
            expect(json['message']).to match(/Invalid credentials/)
          end # it 'returns a failure message' do
        end # context 'When request is invalid' do


      end # describe 'POST /auth/login' do

    end # RSpec.describe AuthenticationController, type: :controller do

I think the only other relevant file is this module:

    module RequestSpecHelper
      # Parse JSON response to ruby hash
      def json
        JSON.parse(response.body)
      end
    end

Thanks for any and all assistance.

Answer 1

Don't manually convert the params to JSON. RSpec does it automatically for you and expects a hash of parameters and not a string.

let(:valid_credentials) do
  { 
    email: user.email, 
    password: user.password 
  }
end

let(:invalid_credentials) do 
  {
    email: Faker::Internet.email,
    password: Faker::Internet.password
  }
end

Additionally for a new project I would skip controller tests and go straight for request specs which are more future proof .