add test to use variable in where_exp condition

test/test_filters.rb

@@ -9,7 +9,7 @@ class TestFilters < JekyllUnitTest
 
     def initialize(opts = {})
       @site = Jekyll::Site.new(opts.merge("skip_config_files" => true))
-      @context = Liquid::Context.new({}, {}, { :site => @site })
+      @context = Liquid::Context.new(@site.site_payload, {}, { :site => @site })
     end
   end
 
@@ -26,12 +26,13 @@ class TestFilters < JekyllUnitTest
 
   context "filters" do
     setup do
-      @filter = make_filter_mock({
-        "timezone" => "UTC",
-        "url"      => "http://example.com",
-        "baseurl"  => "/base",
-      })
       @sample_time = Time.utc(2013, 3, 27, 11, 22, 33)
+      @filter = make_filter_mock({
+        "timezone"               => "UTC",
+        "url"                    => "http://example.com",
+        "baseurl"                => "/base",
+        "dont_show_posts_before" => @sample_time,
+      })
       @sample_date = Date.parse("2013-03-27")
       @time_as_string = "September 11, 2001 12:46:30 -0000"
       @time_as_numeric = 1_399_680_607
@@ -816,6 +817,14 @@ class TestFilters < JekyllUnitTest
         results = @filter.where_exp(SelectDummy.new, "obj", "1 == 1")
         assert_equal [], results
       end
+
+      should "filter by variable values" do
+        @filter.site.tap(&:read)
+        posts = @filter.site.site_payload["site"]["posts"]
+        results = @filter.where_exp(posts, "post",
+          "post.date > site.dont_show_posts_before")
+        assert_equal posts.select { |p| p.date > @sample_time }.count, results.length
+      end
     end
 
     context "group_by_exp filter" do