module ActiveSupport
module Testing
module Assertions
# Test numeric difference between the return value of an expression as a result of what is evaluated
# in the yielded block.
#
# assert_difference 'Article.count' do
# post :create, :article => {...}
# end
#
# An arbitrary expression is passed in and evaluated.
#
# assert_difference 'assigns(:article).comments(:reload).size' do
# post :create, :comment => {...}
# end
#
# An arbitrary positive or negative difference can be specified. The default is +1.
#
# assert_difference 'Article.count', -1 do
# post :delete, :id => ...
# end
#
# An array of expressions can also be passed in and evaluated.
#
# assert_difference [ 'Article.count', 'Post.count' ], +2 do
# post :create, :article => {...}
# end
#
# A error message can be specified.
#
# assert_difference 'Article.count', -1, "An Article should be destroyed" do
# post :delete, :id => ...
# end
def assert_difference(expression, difference = 1, message = nil, &block)
case expression
when String
before = eval(expression, block.send(:binding))
yield
error = "#{expression.inspect} didn't change by #{difference}"
error = "#{message}.\n#{error}" if message
assert_equal(before + difference, eval(expression, block.send(:binding)), error)
when Enumerable
expression.each { |e| assert_difference(e, difference, message, &block) }
else
raise ArgumentError, "Unrecognized expression: #{expression.inspect}"
end
end
# Assertion that the numeric result of evaluating an expression is not changed before and after
# invoking the passed in block.
#
# assert_no_difference 'Article.count' do
# post :create, :article => invalid_attributes
# end
#
# A error message can be specified.
#
# assert_no_difference 'Article.count', "An Article should not be destroyed" do
# post :create, :article => invalid_attributes
# end
def assert_no_difference(expression, message = nil, &block)
assert_difference expression, 0, message, &block
end
end
end
end
