Suggested Workflow

Set the ruby version in .ruby-version to 2.3.5, then perform these steps one by one, fixing errors as they occur:

1) Update gems as listed below, and bundle
2) Boot a Rails console
3) Run Specs with --backtrace option
4) Run Cucumber features (with Geordi's --debug option)
5) When all tests are green, look through your Gemfile and remove as many version constraints as possible

Gem updates

• Replace ruby-debug with byebug or pry
• Replace mysql with mysql2, '< 0.3'
• Remove oniguruma
• Remove net-ssh and net-scp
• Remove fastercsv
• Remove cucumber_spinner
• Remove rspec_spinner
• Update rspec to '< 2'
• Lock haml to '= 3.1.7'
• Unlock andand
• Unlock rake
• Lock test-unit to '= 1.2.3'
• Lock database_cleaner to '< 1.3'
• Lock cucumber to '< 2'
• Lock launchy to '~> 2.1 '
• Lock paperclip to '< 2.8'

• Add capybara-screenshot and require it in Cucumber features. It will simplify debugging failing features.

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  require 'capybara-screenshot/cucumber'
  
  Capybara::Screenshot.prune_strategy = { keep: 12 } # parallel_tests
  

• TODO: Add rspec-patches gem from PH

Code changes

• Remove UTF8 hints at the top of files
• Pay tight attention to method privacy. Ruby 2.3 is more whiny about misusage, especially for Methods defined with define_method.
• Use the spec_label implementation that works in Ruby 2
• Update require statements in features/support/env.rb. Use more require_relative or require Rails.root.join('...')
• Fix Float rounding issues with BigDecimal('12.3')
• Use ' ' for nbsp helper instead of 0xC2.chr + 0xA0.chr
• Remove /s regex modifier (your files are UTF8 anyway
• Remove rcov
• In Rakefile, replace require 'rake/rdoctask' with require 'rdoc/task'

Error: wrong number of arguments (given 1, expected 0)

Use procs instead of lambdas where they are called with variable arguments. Look for named_scopes.

Error: Attempt to call private method, NoMethodError

Fix tests by replacing thing.private_method with thing.send :private_method

will_paginate errors

If you get pagination errors, make sure a collection isn't silently replaced after pagination:

Copy
# does not work
@contracts = @contracts.reject {...}

# works
@contracts.reject! {...}

YAML fixes

• Change

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  # old 
  date:
    order: [ :day, :month, :year ]
    
  # new
  date:
    order:
      - :year
      - :month
      - :day
  

Also see Upgrade from Ruby 1.8.7 to 2.1.5 – an incomplete guide.