accept and clean "false" results

lib/scientist/observation.rb

@@ -38,9 +38,7 @@ def initialize(name, experiment, &block)
   # Return a cleaned value suitable for publishing. Uses the experiment's
   # defined cleaner block to clean the observed value.
   def cleaned_value
-    if value
-      experiment.clean_value value
-    end
+    experiment.clean_value value unless value.nil?
   end
 
   # Is this observation equivalent to another?

test/scientist/observation_test.rb

@@ -88,6 +88,18 @@
       a = Scientist::Observation.new("test", @experiment) { "test" }
       assert_equal "TEST", a.cleaned_value
     end
+
+    it "doesn't clean nil values" do
+      @experiment.clean { |value| "foo" }
+      a = Scientist::Observation.new("test", @experiment) { nil }
+      assert_nil a.cleaned_value
+    end
+
+    it "cleans false values" do
+      @experiment.clean { |value| value.to_s.upcase }
+      a = Scientist::Observation.new("test", @experiment) { false }
+      assert_equal "FALSE", a.cleaned_value
+    end
   end
 
 end