vendor/rails/activesupport/lib/active_support/testing/assertions.rb

   1 module ActiveSupport
   2   module Testing
   3     module Assertions
   4       # Test numeric difference between the return value of an expression as a result of what is evaluated
   5       # in the yielded block.
   6       #
   7       #   assert_difference 'Article.count' do
   8       #     post :create, :article => {...}
   9       #   end
  10       #
  11       # An arbitrary expression is passed in and evaluated.
  12       #
  13       #   assert_difference 'assigns(:article).comments(:reload).size' do
  14       #     post :create, :comment => {...}
  15       #   end
  16       #
  17       # An arbitrary positive or negative difference can be specified. The default is +1.
  18       #
  19       #   assert_difference 'Article.count', -1 do
  20       #     post :delete, :id => ...
  21       #   end
  22       #
  23       # An array of expressions can also be passed in and evaluated.
  24       #
  25       #   assert_difference [ 'Article.count', 'Post.count' ], +2 do
  26       #     post :create, :article => {...}
  27       #   end
  28       #
  29       # A error message can be specified.
  30       #
  31       #   assert_difference 'Article.count', -1, "An Article should be destroyed" do
  32       #     post :delete, :id => ...
  33       #   end
  34       def assert_difference(expression, difference = 1, message = nil, &block)
  35         b = block.send(:binding)
  36         exps = Array.wrap(expression)
  37         before = exps.map { |e| eval(e, b) }
  38
  39         yield
  40
  41         exps.each_with_index do |e, i|
  42           error = "#{e.inspect} didn't change by #{difference}"
  43           error = "#{message}.\n#{error}" if message
  44           assert_equal(before[i] + difference, eval(e, b), error)
  45         end
  46       end
  47
  48       # Assertion that the numeric result of evaluating an expression is not changed before and after
  49       # invoking the passed in block.
  50       #
  51       #   assert_no_difference 'Article.count' do
  52       #     post :create, :article => invalid_attributes
  53       #   end
  54       #
  55       # A error message can be specified.
  56       #
  57       #   assert_no_difference 'Article.count', "An Article should not be destroyed" do
  58       #     post :create, :article => invalid_attributes
  59       #   end
  60       def assert_no_difference(expression, message = nil, &block)
  61         assert_difference expression, 0, message, &block
  62       end
  63     end
  64   end
  65 end