snippetsmania.com
Post and share your code snippets

module AssertHelper
# Author:: <a href="http://blog.caboo.se/articles/2006/06/13/a-better-assert_difference" >http://blog.caboo.se/articles/2006/06/13/a-better-assert_difference</a>
#
# == Examples
#   assert_difference Group, :count do
#     post :create, :group => { :name => 'monkeys' }
#   end
#
#   assert_difference [ User, Group ], :count do
#     Membership.create(:user_id => 1, :group_id => 5)
#   end
#
#   assert_difference User, :name, nil do
#     post :update, :id => 5, { :name => 'monkeys' }
#   end
def assert_difference(objects, method = nil, difference = 1)
objects = [objects].flatten
initial_values = objects.inject([]) { |sum,obj| sum << obj.send(method) }
yield
if difference.nil?
objects.each_with_index { |obj,i|
assert_not_equal initial_values[i], obj.send(method), "#{obj}##{method}"
}
else
objects.each_with_index { |obj,i|
assert_equal initial_values[i] + difference, obj.send(method), "#{obj}##{method}"
}
end
end

def assert_no_difference_in_size(object, methods = nil, &block)
assert_difference_in_size object, methods, 0, &block
end
end

source