adds the simple object dependency

where the next object is dependent on the previous one
and just behind it, the padded_length away

test/risc/position/test_object_listener.rb

@@ -0,0 +1,34 @@
+require_relative "../helper"
+
+module Risc
+  module Position
+    class Dummy
+      def padded_length
+        4
+      end
+    end
+    class TestObjectListener < MiniTest::Test
+
+      def setup
+        @object = Dummy.new
+        @dependent = Dummy.new
+        @pos = Position.set(@object,0)
+        Position.set(@dependent,0)
+        @listener = ObjectListener.new(@dependent)
+      end
+      def test_register
+        assert @pos.register_event(:position_changed , @listener)
+      end
+      def test_no_fire
+        @pos.register_event(:position_changed , self)
+        @pos = Position.set(@object,0)
+        assert_equal 0 , Position.get(@dependent).at
+      end
+      def test_reset
+        @pos.register_event(:position_changed , @listener)
+        @pos = Position.set(@object,4)
+        assert_equal 4 , Position.get(@dependent).at
+      end
+    end
+  end
+end