global fixtures are evil, but we’ve got a bunch of unit tests depending on them, so we still need them around

here’s a neat [and generally fast, though a degenerate O(#tables^2) case is possible] way of deleting all fixtures without invoking db dependent ways of ignoring foreign-key constraints, and without loading all the objects into memory :

classes = ActiveRecord::Base.connection.tables.map {|t|
  t.singularize.camelize.constantize rescue nil
}.compact.reject{|cls| !cls.ancestors.include?(ActiveRecord::Base)}

while classes.size > 0
  classes = classes.select{|c|
    begin
      c.delete_all
      false
    rescue
      true
    end
  }.reverse!
end