move assignment test into own dir

test/mom/assign/test_assign_arg_const.rb

@@ -0,0 +1,32 @@
+require_relative '../helper'
+
+module Risc
+  class TestAssignArgConst < MiniTest::Test
+    include Statements
+
+    def setup
+      super
+      @input = "arg = 5"
+      @expect = [LoadConstant, SlotToReg, RegToSlot]
+    end
+    def test_local_assign_instructions
+      assert_nil msg = check_nil , msg
+    end
+
+    def test_constant_load
+      produced = produce_body
+      assert_equal 5 , produced.constant.known_object.value
+    end
+
+    def test_slot_move
+      produced = produce_body
+      assert_equal produced.next(2).register , produced.register
+    end
+    def test_load_args_from_message
+      produced = produce_body
+      assert_equal :r0 , produced.next.array.symbol , produced.next.to_rxf
+      assert_equal 9 , produced.next.index , produced.next.to_rxf
+    end
+
+  end
+end