Add tests for using custom excerpt

test/source/_posts/2013-04-11-custom-excerpt.markdown

@@ -0,0 +1,8 @@
+---
+layout: ~
+excerpt: 'I can set a custom excerpt with *markdown*'
+---
+
+This is not my excerpt.
+
+Neither is this.

test/test_generated_site.rb

@@ -14,7 +14,7 @@ class TestGeneratedSite < Test::Unit::TestCase
     end
 
     should "ensure post count is as expected" do
-      assert_equal 31, @site.posts.size
+      assert_equal 32, @site.posts.size
     end
 
     should "insert site.posts into the index" do

test/test_post.rb

@@ -320,6 +320,21 @@ class TestPost < Test::Unit::TestCase
             assert !@post.excerpt.include?("---"), "does not contains separator"
           end
         end
+
+        context "with custom excerpt" do
+          setup do
+	    file = "2013-04-11-custom-excerpt.markdown"
+	    @post.process(file)
+            @post.read_yaml(@source, file)
+            @post.transform
+	  end
+
+          should "use custom excerpt" do
+	    assert_equal("<p>I can set a custom excerpt with <em>markdown</em></p>", @post.excerpt)
+	  end
+
+	end
+
       end
     end