lots of stuff to move to linked lists

and remove the blocks
more position stuff coming, but the list part should be ok

test/register/test_all.rb

@@ -2,3 +2,4 @@
 require_relative "test_compat"
 require_relative "test_padding"
 require_relative "test_positioning"
+require_relative "test_instructions"

test/register/test_instructions.rb

@@ -0,0 +1,46 @@
+require_relative "../helper"
+
+module Register
+  class TestInstructions < MiniTest::Test
+    def setup
+      @label = Label.new(nil , "test")
+      @branch = Branch.new(nil , @label)
+      @instruction = Instruction.new(nil)
+    end
+    def test_last_empty
+      assert_equal @instruction, @instruction.last
+    end
+    def test_last_not_empty
+      @instruction.set_next @branch
+      assert_equal @branch, @instruction.last
+    end
+    def test_append_empty
+      @instruction.append @branch
+      assert_equal @branch, @instruction.last
+    end
+    def test_insert
+      @instruction.insert @branch
+      assert_equal @branch, @instruction.last
+    end
+    def test_append_not_empty
+      @instruction.append @branch
+      @instruction.append @label
+      assert_equal @label, @instruction.last
+    end
+    def test_next1
+      assert_equal nil , @instruction.next
+    end
+    def test_next2
+      @instruction.set_next @label
+      assert_equal @label , @instruction.next
+      assert_equal nil , @instruction.next(2)
+    end
+    def test_replace
+      @instruction.append @branch
+      @instruction.replace_next @label
+      assert_equal @label, @instruction.last
+      assert_equal @label, @instruction.next
+      assert_equal 2 , @instruction.length , @instruction.to_ac
+    end
+  end
+end