1 files changed, 97 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/testing/assertions.rb b/activesupport/lib/active_support/testing/assertions.rb
new file mode 100644
index 0000000000..11cca82995
--- /dev/null
+++ b/activesupport/lib/active_support/testing/assertions.rb
@@ -0,0 +1,97 @@
+require 'active_support/core_ext/object/blank'
+
+module ActiveSupport
+  module Testing
+    module Assertions
+      # Assert that an expression is not truthy. Passes if <tt>object</tt> is
+      # +nil+ or +false+. "Truthy" means "considered true in a conditional"
+      # like <tt>if foo</tt>.
+      #
+      #   assert_not nil    # => true
+      #   assert_not false  # => true
+      #   assert_not 'foo'  # => Expected "foo" to be nil or false
+      #
+      # An error message can be specified.
+      #
+      #   assert_not foo, 'foo should be false'
+      def assert_not(object, message = nil)
+        message ||= "Expected #{mu_pp(object)} to be nil or false"
+        assert !object, message
+      end
+
+      # 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 <tt>1</tt>.
+      #
+      #   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 lambda or a list of lambdas can be passed in and evaluated:
+      #
+      #   assert_difference ->{ Article.count }, 2 do
+      #     post :create, article: {...}
+      #   end
+      #
+      #   assert_difference [->{ Article.count }, ->{ Post.count }], 2 do
+      #     post :create, article: {...}
+      #   end
+      #
+      # An 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)
+        expressions = Array(expression)
+
+        exps = expressions.map { |e|
+          e.respond_to?(:call) ? e : lambda { eval(e, block.binding) }
+        }
+        before = exps.map { |e| e.call }
+
+        yield
+
+        expressions.zip(exps).each_with_index do |(code, e), i|
+          error  = "#{code.inspect} didn't change by #{difference}"
+          error  = "#{message}.\n#{error}" if message
+          assert_equal(before[i] + difference, e.call, error)
+        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
+      #
+      # An error message can be specified.
+      #
+      #   assert_no_difference 'Article.count', 'An Article should not be created' 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