kisselbug - when you get your if-condition the wrong way round.... As epitomised almost daily by the Great Indigenous Ijonous as he traversed the frozen wastelands of Software Development.

gistfile1.rb

class Kisselbugger
  
  def something_that_evaluates_to_true
    # ...
  end

  def decide_and_do_something
    # several hours of looking at line 9 results in a: "AArgh, ya wee bugger. Not again!"
    if not something_that_evaluates_to_true
      do_the_true_response
    else
      do_the_false_response
    end   
  end
  
  def do_the_true_response
    # ...
  end

  def do_the_false_response
    # ...
  end
  
end