Add tests for determining source dir

lib/jekyll/layout_reader.rb

@@ -45,7 +45,7 @@ module Jekyll
     def layout_directory_in_cwd
       # TODO: Fix on Windows
       dir = File.join(Dir.pwd, File.expand_path(site.config['layouts'], '/'))
-      if Directory.exists?(dir)
+      if File.directory?(dir)
         dir
       else
         nil

test/test_layout_reader.rb

@@ -13,5 +13,22 @@ class TestLayoutReader < Test::Unit::TestCase
       layouts = LayoutReader.new(@site).read
       assert_equal ["default", "simple", "post/simple"].sort, layouts.keys.sort
     end
+
+    context "when no _layouts directory exists in CWD" do
+      should "know to use the layout directory relative to the site source" do
+        assert_equal LayoutReader.new(@site).send(:layout_directory), source_dir("_layouts")
+      end
+    end
+
+    context "when a _layouts directory exists in CWD" do
+      setup do
+        stub(File).directory? { true }
+        stub(Dir).pwd { source_dir("blah") }
+      end
+
+      should "know to use the layout directory relative to CWD" do
+        assert_equal LayoutReader.new(@site).send(:layout_directory), source_dir("blah/_layouts")
+      end
+    end
   end
 end