diff --git a/src/opcode.nim b/src/opcode.nim
index 7c6bdabf3..a5c2e94ab 100644
--- a/src/opcode.nim
+++ b/src/opcode.nim
@@ -4,6 +4,7 @@ import
 
 template run*(opcode: Opcode, computation: var BaseComputation) =
   # Hook for performing the actual VM execution
+  # opcode.consumeGas(computation)
   computation.gasMeter.consumeGas(opcode.gasCost(computation), reason = $opcode.kind)
   opcode.runLogic(computation)
 
diff --git a/tests/memory_test.nim b/tests/memory_test.nim
index 60e016b0d..e9ac1fc0e 100644
--- a/tests/memory_test.nim
+++ b/tests/memory_test.nim
@@ -2,23 +2,23 @@ import unittest, macros, strformat, strutils, sequtils, constants, opcode_values
 
 proc memory32: Memory =
   result = newMemory()
-  result.extend(0.i256, 32.i256)
+  result.extend(0.u256, 32.u256)
 
 proc memory128: Memory =
   result = newMemory()
-  result.extend(0.i256, 128.i256)
+  result.extend(0.u256, 128.u256)
 
 suite "memory":
   test "write":
     var mem = memory32()
     # Test that write creates 32byte string == value padded with zeros
-    mem.write(startPosition = 0.i256, size = 4.i256, value = @[1.byte, 0.byte, 1.byte, 0.byte])
+    mem.write(startPosition = 0.u256, size = 4.u256, value = @[1.byte, 0.byte, 1.byte, 0.byte])
     check(mem.bytes == @[1.byte, 0.byte, 1.byte, 0.byte].concat(repeat(0.byte, 28)))
 
-  test "write rejects invalid position":
-    expect(ValidationError):
-      var mem = memory32()
-      mem.write(startPosition = -1.i256, size = 2.i256, value = @[1.byte, 0.byte])
+  # test "write rejects invalid position":
+  #   expect(ValidationError):
+  #     var mem = memory32()
+  #     mem.write(startPosition = -1.i256, size = 2.i256, value = @[1.byte, 0.byte])
     # expect(ValidationError):
       # TODO: work on 256
       # var mem = memory32()
@@ -26,38 +26,38 @@ suite "memory":
       # mem.write(startPosition = pow(2.i256, 256), size = 2.i256, value = @[1.byte, 0.byte])
 
   test "write rejects invalid size":
-    expect(ValidationError):
-      var mem = memory32()  
-      mem.write(startPosition = 0.i256, size = -1.i256, value = @[1.byte, 0.byte])
+    # expect(ValidationError):
+    #   var mem = memory32()  
+    #   mem.write(startPosition = 0.i256, size = -1.i256, value = @[1.byte, 0.byte])
     expect(ValidationError):
       var mem = memory32()
-      mem.write(startPosition = 0.i256, size = pow(2.i256, 256), value = @[1.byte, 0.byte])
+      mem.write(startPosition = 0.u256, size = pow(2.u256, 256), value = @[1.byte, 0.byte])
 
   test "write rejects invalid value":
     expect(ValidationError):
       var mem = memory32()
-      mem.write(startPosition = 0.i256, size = 4.i256, value = @[1.byte, 0.byte])
+      mem.write(startPosition = 0.u256, size = 4.u256, value = @[1.byte, 0.byte])
   
   test "write rejects valyes beyond memory size":
     expect(ValidationError):
       var mem = memory128()
-      mem.write(startPosition = 128.i256, size = 4.i256, value = @[1.byte, 0.byte, 1.byte, 0.byte])
+      mem.write(startPosition = 128.u256, size = 4.u256, value = @[1.byte, 0.byte, 1.byte, 0.byte])
 
   test "extends appropriately extends memory":
     var mem = newMemory()
     # Test extends to 32 byte array: 0 < (start_position + size) <= 32
-    mem.extend(startPosition = 0.i256, size = 10.i256)
+    mem.extend(startPosition = 0.u256, size = 10.u256)
     check(mem.bytes == repeat(0.byte, 32))
     # Test will extend past length if params require: 32 < (start_position + size) <= 64
-    mem.extend(startPosition = 28.i256, size = 32.i256)
+    mem.extend(startPosition = 28.u256, size = 32.u256)
     check(mem.bytes == repeat(0.byte, 64))
     # Test won't extend past length unless params require: 32 < (start_position + size) <= 64
-    mem.extend(startPosition = 48.i256, size = 10.i256)
+    mem.extend(startPosition = 48.u256, size = 10.u256)
     check(mem.bytes == repeat(0.byte, 64))
 
   test "read returns correct bytes":
     var mem = memory32()
-    mem.write(startPosition = 5.i256, size = 4.i256, value = @[1.byte, 0.byte, 1.byte, 0.byte])
-    check(mem.read(startPosition = 5.i256, size = 4.i256) == @[1.byte, 0.byte, 1.byte, 0.byte])
-    check(mem.read(startPosition = 6.i256, size = 4.i256) == @[0.byte, 1.byte, 0.byte, 0.byte])
-    check(mem.read(startPosition = 1.i256, size = 3.i256) == @[0.byte, 0.byte, 0.byte])
+    mem.write(startPosition = 5.u256, size = 4.u256, value = @[1.byte, 0.byte, 1.byte, 0.byte])
+    check(mem.read(startPosition = 5.u256, size = 4.u256) == @[1.byte, 0.byte, 1.byte, 0.byte])
+    check(mem.read(startPosition = 6.u256, size = 4.u256) == @[0.byte, 1.byte, 0.byte, 0.byte])
+    check(mem.read(startPosition = 1.u256, size = 3.u256) == @[0.byte, 0.byte, 0.byte])