data_controller_test.rb

require 'test_helper'

class DataControllerTest < ActionController::TestCase

  test "should create data" do
    assert_difference('Data.count') do
      post '/data', { # Same error when replaced with /datum
                        name: 'my_name',
                      },
                      {
                        HTTP_CONTENT_TYPE: 'application/json',
                        HTTP_ACCEPT: 'application/vnd.api-test+json; version=1'
                      }
    end

    assert_response 201
  end
end