move assignment test into own dir

test/mom/assign/test_assign_arg_const.rb

@@ -1,4 +1,4 @@
-require_relative 'helper'
+require_relative '../helper'
 
 module Risc
   class TestAssignArgConst < MiniTest::Test

test/mom/assign/test_assign_ivar_const.rb

@@ -1,4 +1,4 @@
-require_relative 'helper'
+require_relative '../helper'
 
 module Risc
   class TestAssignIvarConst < MiniTest::Test

test/mom/assign/test_assign_local_arg.rb

@@ -1,4 +1,4 @@
-require_relative 'helper'
+require_relative '../helper'
 
 module Risc
   class TestAssignLocalArg < MiniTest::Test

test/mom/assign/test_assign_local_const.rb

@@ -1,4 +1,4 @@
-require_relative 'helper'
+require_relative '../helper'
 
 module Risc
   class TestAssignLocalConst < MiniTest::Test

test/mom/assign/test_assign_local_ivar.rb

@@ -1,4 +1,4 @@
-require_relative 'helper'
+require_relative '../helper'
 
 module Risc
   class TestAssignLocalIvar < MiniTest::Test

test/mom/assign/test_assign_local_send.rb

@@ -1,4 +1,4 @@
-require_relative 'helper'
+require_relative '../helper'
 
 module Risc
   class TestAssignLocalSend < MiniTest::Test