Simplify tests for older test/unit

Author: jbarnette

test/html/pipeline/syntax_highlight_filter_test.rb

@@ -8,15 +8,15 @@ def test_highlight_default
       "<pre>hello</pre>", :highlight => "coffeescript"
 
     doc = filter.call
-    assert_not_empty doc.css ".highlight-coffeescript"
+    assert !doc.css(".highlight-coffeescript").empty?
   end
 
   def test_highlight_default_will_not_override
     filter = SyntaxHighlightFilter.new \
       "<pre lang='c'>hello</pre>", :highlight => "coffeescript"
 
     doc = filter.call
-    assert_empty doc.css ".highlight-coffeescript"
-    assert_not_empty doc.css ".highlight-c"
+    assert doc.css(".highlight-coffeescript").empty?
+    assert !doc.css(".highlight-c").empty?
   end
 end