Allow Hash with default value or default proc to be used

test/variable_test.rb

@@ -157,4 +157,16 @@ class VariableResolutionTest < Test::Unit::TestCase
     assert_equal 'bazbar', template.render
   end
 
+  def test_hash_with_default_proc
+    template = Template.parse(%|Hello {{ test }}|)
+    assigns = Hash.new { |h,k| raise "Unknown variable '#{k}'" }
+    assigns['test'] = 'Tobi'
+    assert_equal 'Hello Tobi', template.render!(assigns)
+    assigns.delete('test')
+    e = assert_raises(RuntimeError) {
+      template.render!(assigns)
+    }
+    assert_equal "Unknown variable 'test'", e.message
+  end
+
 end