Updated should_change and should_not_change to accept a string descri…

…ption and a block [#154]

lib/shoulda/macros.rb

@@ -3,65 +3,67 @@
 module Shoulda # :nodoc:
   module Macros
     # Macro that creates a test asserting a change between the return value
-    # of an expression that is run before and after the current setup block
+    # of a block that is run before and after the current setup block
     # is run. This is similar to Active Support's <tt>assert_difference</tt>
     # assertion, but supports more than just numeric values.  See also
     # should_not_change.
     #
+    # The passed description will be used when generating the test name and failure messages.
+    #
     # Example:
     #
     #   context "Creating a post" do
     #     setup { Post.create }
-    #     should_change "Post.count", :by => 1
+    #     should_change("the number of posts", :by => 1) { Post.count }
     #   end
     #
     # As shown in this example, the <tt>:by</tt> option expects a numeric
     # difference between the before and after values of the expression.  You
     # may also specify <tt>:from</tt> and <tt>:to</tt> options:
     #
-    #   should_change "Post.count", :from => 0, :to => 1
-    #   should_change "@post.title", :from => "old", :to => "new"
+    #   should_change("the number of posts", :from => 0, :to => 1) { Post.count }
+    #   should_change("the post title", :from => "old", :to => "new") { @post.title }
     #
     # Combinations of <tt>:by</tt>, <tt>:from</tt>, and <tt>:to</tt> are allowed:
     #
-    #   should_change "@post.title"                # => assert the value changed in some way
-    #   should_change "@post.title", :from => "old" # => assert the value changed to anything other than "old"
-    #   should_change "@post.title", :to   => "new" # => assert the value changed from anything other than "new"
-    def should_change(expression, options = {})
+    #   should_change("the post title") { @post.title }                 # => assert the value changed in some way
+    #   should_change("the post title", :from => "old") { @post.title } # => assert the value changed to anything other than "old"
+    #   should_change("the post title", :to   => "new") { @post.title } # => assert the value changed from anything other than "new"
+    def should_change(description, options = {}, &block)
       by, from, to = get_options!([options], :by, :from, :to)
-      stmt = "change #{expression.inspect}"
+      stmt = "change #{description}"
       stmt << " from #{from.inspect}" if from
       stmt << " to #{to.inspect}" if to
       stmt << " by #{by.inspect}" if by
 
-      expression_eval = lambda { eval(expression) }
-      before = lambda { @_before_should_change = expression_eval.bind(self).call }
+      before = lambda { @_before_should_change = block.bind(self).call }
       should stmt, :before => before do
         old_value = @_before_should_change
-        new_value = expression_eval.bind(self).call
-        assert_operator from, :===, old_value, "#{expression.inspect} did not originally match #{from.inspect}" if from
-        assert_not_equal old_value, new_value, "#{expression.inspect} did not change" unless by == 0
-        assert_operator to, :===, new_value, "#{expression.inspect} was not changed to match #{to.inspect}" if to
+        new_value = block.bind(self).call
+        assert_operator from, :===, old_value, "#{description} did not originally match #{from.inspect}" if from
+        assert_not_equal old_value, new_value, "#{description} did not change" unless by == 0
+        assert_operator to, :===, new_value, "#{description} was not changed to match #{to.inspect}" if to
         assert_equal old_value + by, new_value if by
       end
     end
 
     # Macro that creates a test asserting no change between the return value
-    # of an expression that is run before and after the current setup block
+    # of a block that is run before and after the current setup block
     # is run. This is the logical opposite of should_change.
     #
+    # The passed description will be used when generating the test name and failure message.
+    #
     # Example:
     #
     #   context "Updating a post" do
     #     setup { @post.update_attributes(:title => "new") }
-    #     should_not_change "Post.count"
+    #     should_not_change("the number of posts") { Post.count }
     #   end
-    def should_not_change(expression)
-      expression_eval = lambda { eval(expression) }
-      before = lambda { @_before_should_not_change = expression_eval.bind(self).call }
-      should "not change #{expression.inspect}", :before => before do
-        new_value = expression_eval.bind(self).call
-        assert_equal @_before_should_not_change, new_value, "#{expression.inspect} changed"
+    def should_not_change(description, &block)
+      before = lambda { @_before_should_not_change = block.bind(self).call }
+      should "not change #{description}", :before => before do
+        new_value = block.bind(self).call
+        assert_equal @_before_should_not_change, new_value, "#{description} changed"
       end
     end
 

test/other/helpers_test.rb

@@ -88,24 +88,24 @@ class HelpersTest < ActiveSupport::TestCase # :nodoc:
         @a.push(4)
       end
 
-      should_change "@a.length", :by => 1
-      should_change "@a.length", :from => 3
-      should_change "@a.length", :to => 4
-      should_change "@a[0]", :by => 0
-      should_not_change "@a[0]"
+      should_change("the number of elements", :by => 1) { @a.length }
+      should_change("the number of elements", :from => 3) { @a.length }
+      should_change("the number of elements", :to => 4) { @a.length }
+      should_change("the first element", :by => 0) { @a[0] }
+      should_not_change("the first element") { @a[0] }
     end
 
     context "after replacing it with an array of strings" do
       setup do
         @a = %w(a b c d e f)
       end
 
-      should_change "@a.length", :by => 3
-      should_change "@a.length", :from => 3, :to => 6, :by => 3
-      should_change "@a[0]"
-      should_change "@a[1]", :from => 2, :to => "b"
-      should_change "@a[2]", :from => /\d/, :to => /\w/
-      should_change "@a[3]", :to => String
+      should_change("the number of elements", :by => 3) { @a.length }
+      should_change("the number of elements", :from => 3, :to => 6, :by => 3) { @a.length }
+      should_change("the first element") { @a[0] }
+      should_change("the second element", :from => 2, :to => "b") { @a[1] }
+      should_change("the third element", :from => /\d/, :to => /\w/) { @a[2] }
+      should_change("the last element", :to => String) { @a[3] }
     end
   end