Rails traps into which I fall every damn time

• If the return value of a method in your tests is totally different from what you see in the source code, chances are 100:1 that you (or your colleague) stubbed it out before the test run
• You can’t set the sequence of validations in ActiveRecord. You just can’t. Don’t add validations that depend on each other, e.g. ensuring the presence of X in one validation and in another that X > Y.
• Be carefull where you use symbols. Something like

  belongs_to :preferred_city, :class_name => City, :foreign_key => :city_id
  

  will throw something like

  NoMethodError: undefined method `match’ for #

  because you must use strings here a la:

  belongs_to :preferred_city, :class_name => 'City', :foreign_key => 'city_id'
  

• If you have trouble saving a model via web interface for no obvious reason double check the log, there’s a good chance that you forgot to use attr_accessble
• Similar to above: If you use nested forms e.g. User has_one profile and your editing user and profile in one form don’t forget

  attr_accessible :profile_attributes
  

  in your user model

• When manually constructing links like:

   def my_url
      "/offer/#{city.to_param}"
   end
  

  don’t forget the leading slash unless you really want a relative path.

• Formtastic is great, but I always forget that it’s

  form.input :field, :input_html => ...
  

  and not

  form.input :field, :html => ...
  

  and it’s

  form.button :commit, :button_html => ...
  

  and not

  form.button :commit, :html => ...
  

• I constantly forget to interpolate strings in regexes, so given

  pattern = 'oh no'
  

  I find myself writing

  if input =~ /pattern/
  

  instead of

  if input =~ /#{pattern}/
  

• When you pass numeric values to cucumber steps make sure to call to_i, to_f or whatever is appropriate because cucumber passes everything as a string (yes, an easy one, but I forget it every now and then)