Gist to troubleshoot https://github.com/modeset/teaspoon/issues/120#issuecomment-26818114 Patch to be applied on a fresh Rails 4 project. teaspoon gem is pointing to a local checkout of the repo at rev https://github.com/modeset/teaspoon/tree/b5baaf387f87537bda64f2894563ab2d7ef9807b

teaspoon-err-rails4.patch

diff --git a/Gemfile b/Gemfile
index 30d54d4..5461168 100644
--- a/Gemfile
+++ b/Gemfile
@@ -43,3 +43,13 @@ end
 
 # Use debugger
 # gem 'debugger', group: [:development, :test]
+
+# Get some nice better errors on development
+group :development do
+  gem 'better_errors'
+end
+
+group :development, :test do
+  gem "teaspoon", path: '~/src/teaspoon'
+end
+
diff --git a/Gemfile.lock b/Gemfile.lock
index 7cab85a..221bf43 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,3 +1,10 @@
+PATH
+  remote: ~/src/teaspoon
+  specs:
+    teaspoon (0.7.7)
+      phantomjs (>= 1.8.1.1)
+      railties (>= 3.2.5, < 5)
+
 GEM
   remote: https://rubygems.org/
   specs:
@@ -27,7 +34,18 @@ GEM
       tzinfo (~> 0.3.37)
     arel (4.0.0)
     atomic (1.1.14)
+    better_errors (1.0.1)
+      coderay (>= 1.0.0)
+      erubis (>= 2.6.6)
     builder (3.1.4)
+    capybara (2.1.0)
+      mime-types (>= 1.16)
+      nokogiri (>= 1.3.3)
+      rack (>= 1.0.0)
+      rack-test (>= 0.5.4)
+      xpath (~> 2.0)
+    cliver (0.2.2)
+    coderay (1.0.9)
     coffee-rails (4.0.1)
       coffee-script (>= 2.2.0)
       railties (>= 4.0.0, < 5.0)
@@ -50,8 +68,18 @@ GEM
       mime-types (~> 1.16)
       treetop (~> 1.4.8)
     mime-types (1.25)
+    mini_portile (0.5.1)
     minitest (4.7.5)
     multi_json (1.8.2)
+    nokogiri (1.6.0)
+      mini_portile (~> 0.5.0)
+    phantomjs (1.8.1.1)
+      poltergeist
+    poltergeist (1.4.1)
+      capybara (~> 2.1.0)
+      cliver (~> 0.2.1)
+      multi_json (~> 1.0)
+      websocket-driver (>= 0.2.0)
     polyglot (0.3.3)
     rack (1.5.2)
     rack-test (0.6.2)
@@ -103,11 +131,15 @@ GEM
     uglifier (2.2.1)
       execjs (>= 0.3.0)
       multi_json (~> 1.0, >= 1.0.2)
+    websocket-driver (0.3.0)
+    xpath (2.0.0)
+      nokogiri (~> 1.3)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
+  better_errors
   coffee-rails (~> 4.0.0)
   jbuilder (~> 1.2)
   jquery-rails
@@ -115,5 +147,6 @@ DEPENDENCIES
   sass-rails (~> 4.0.0)
   sdoc
   sqlite3
+  teaspoon!
   turbolinks
   uglifier (>= 1.3.0)
diff --git a/app/assets/javascripts/application.js b/app/assets/javascripts/application.js
index d6925fa..5f461e2 100644
--- a/app/assets/javascripts/application.js
+++ b/app/assets/javascripts/application.js
@@ -1,16 +1 @@
-// This is a manifest file that'll be compiled into application.js, which will include all the files
-// listed below.
-//
-// Any JavaScript/Coffee file within this directory, lib/assets/javascripts, vendor/assets/javascripts,
-// or vendor/assets/javascripts of plugins, if any, can be referenced here using a relative path.
-//
-// It's not advisable to add code directly here, but if you do, it'll appear at the bottom of the
-// compiled file.
-//
-// Read Sprockets README (https://github.com/sstephenson/sprockets#sprockets-directives) for details
-// about supported directives.
-//
-//= require jquery
-//= require jquery_ujs
-//= require turbolinks
-//= require_tree .
+//= require non_extisting_file
diff --git a/config/environments/development.rb b/config/environments/development.rb
index d6f87b5..771e757 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -7,7 +7,7 @@ TeaspoonErr::Application.configure do
   config.cache_classes = false
 
   # Do not eager load code on boot.
-  config.eager_load = false
+  config.eager_load = true
 
   # Show full error reports and disable caching.
   config.consider_all_requests_local       = true