undefined method `+' for nil:NilClass (NoMethodError)

When Capybara/Cucumber tests fail: ```ruby undefined method `+' for nil:NilClass (NoMethodError) .../.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/minitest-5.10.1/lib/minitest/assertions.rb:135:in `assert' ``` Do this: 1. Install test-unit ```ruby gem 'test-unit' ``` 2. Include assertions in env.rb ```ruby World Test::Unit::Assertions ```