new assertion: assert_blank

Signed-off-by: NXavier Noria <fxn@hashref.com>

activesupport/lib/active_support/testing/assertions.rb

@@ -62,6 +62,13 @@ def assert_difference(expression, difference = 1, message = nil, &block)
       def assert_no_difference(expression, message = nil, &block)
         assert_difference expression, 0, message, &block
       end
+      
+      # Test if an expression is blank. Passes if object.blank? is true.
+      #
+      #   assert_blank [] # => true
+      def assert_blank(object)
+        assert object.blank?, "#{object.inspect} is not blank"
+      end
     end
   end
 end

activesupport/test/test_test.rb

@@ -86,6 +86,34 @@ def default_test; end
   end
 end
 
+class EmptyTrue
+  def empty?() true; end
+end
+
+class EmptyFalse
+  def empty?() false; end
+end
+
+class AssertBlankTest < ActiveSupport::TestCase
+  BLANK = [ EmptyTrue.new, nil, false, '', '   ', "  \n\t  \r ", [], {} ]
+  NOT_BLANK   = [ EmptyFalse.new, Object.new, true, 0, 1, 'j', [nil], { nil => 0 } ]
+  
+  def test_assert_blank_true
+    BLANK.each { |v| assert_blank v }
+  end
+  
+  def test_assert_blank_false
+    NOT_BLANK.each { |v|
+      begin 
+        assert_blank v
+        fail 'should not get to here'
+      rescue Exception => e
+        assert_match(/is not blank/, e.message) 
+      end  
+    }
+  end
+end
+
 # These should always pass
 if ActiveSupport::Testing.const_defined?(:Default)
   class NotTestingThingsTest < Test::Unit::TestCase