Rack Parser Regression

benchmark.rb

# Before
Calculating -------------------------------------
                 GET        35 i/100ms
                POST        34 i/100ms
-------------------------------------------------
                 GET      357.4 (±3.4%) i/s -       1785 in   4.999583s
                POST      341.5 (±3.8%) i/s -       1734 in   5.084699s

# After
Calculating -------------------------------------
                 GET        23 i/100ms
                POST        23 i/100ms
-------------------------------------------------
                 GET      242.5 (±3.3%) i/s -       1219 in   5.032013s
                POST      235.2 (±3.4%) i/s -       1196 in   5.091327s

user_flow_test.rb

require 'test_helper'
require 'benchmark/ips'

class UserFlowTest < ActionDispatch::IntegrationTest
  def test_get
    get "/users"
    assert_equal 200, response.status
  end

  def test_post
    post "/users", { user: { first_name: 'Alan', last_name: 'Tan' } }
    assert_equal 302, response.status
  end
end

Benchmark.ips(5) do |bm|
  bm.report 'GET Integration Test' do
    Minitest.run_one_method(UserFlowTest, 'test_get')
  end

  bm.report 'POST Integration Test' do
    Minitest.run_one_method(UserFlowTest, 'test_post')
  end
end

users_controller.rb

class UsersController < ApplicationController
  def index
    @users = User.all
  end

  def create
    @user = User.new(user_params)

    if @user.save
      flash[:success] = 'User was successfully created.'
      redirect_to @user
    else
      render 'new'
    end
  end
end