set up ivar_assignment correctly

for statement tests
and write mom tests
also implement to_mom
and fix local (self) bug

test/vool/to_mom/test_local.rb

@@ -2,21 +2,13 @@ require_relative "helper"
 
 module Vool
   class TestLocalMom < MiniTest::Test
-    include CompilerHelper
+    include MomCompile
 
     def setup
       Risc.machine.boot
       @method = compile_first_method( "a = 5")
     end
 
-    def compile_first_method input
-      lst = VoolCompiler.compile as_main( input )
-      assert_equal Parfait::Class , lst.clazz.class , input
-      method = lst.clazz.get_method(:main)
-      assert method
-      lst.to_mom( nil ).first
-    end
-
     def test_class_compiles
       assert_equal Mom::SlotConstant , @method.first.class , @method
     end
@@ -27,7 +19,7 @@ module Vool
       assert_equal :message , @method.first.left[0]
     end
     def test_slot_gets_self
-      assert_equal :self , @method.first.left[1]
+      assert_equal :frame , @method.first.left[1]
     end
     def test_slot_assigns_to_local
       assert_equal :a , @method.first.left[-1]