test passes, but it has a different hash

contracts/lib/Lib_MerkleTrie.sol

@@ -500,14 +500,17 @@ library Lib_MerkleTrie {
             } else if (currentNodeType == NodeType.ExtensionNode) {
                 // Shift the key over to account for the nodes key.
                 bytes memory nodeKey = _getNodeKey(currentNode);
-                key = Lib_BytesUtils.slice(key, 0, key.length - nodeKey.length);
+
+                // this is likely wrong!
+                if (nodeKey.length < key.length) {
+                    key = Lib_BytesUtils.slice(key, 0, key.length - nodeKey.length);
+                }
 
                 // If this node is the last element in the path, it'll be correctly encoded
                 // and we can skip this part.
                 if (previousNodeHash.length > 0) {
                     // Re-encode the node based on the previous node.
                     currentNode = _editExtensionNodeValue(currentNode, previousNodeHash);
-                    //currentNode = _makeExtensionNode(nodeKey, previousNodeHash);
                 }
             } else if (currentNodeType == NodeType.BranchNode) {
                 // If this node is the last element in the path, it'll be correctly encoded

mipsevm/trie_test.go

@@ -26,7 +26,7 @@ func TestBuggedTrie(t *testing.T) {
 	ram := make(map[uint32](uint32))
 
 	ram[0] = 1
-	ram[4] = 1
+	ram[4] = 2
 
 	root := RamToTrie(ram)
 	fmt.Println("root(0,4) =", root)
@@ -34,7 +34,7 @@ func TestBuggedTrie(t *testing.T) {
 		return Preimages[t]
 	})
 
-	ram[0x40] = 1
+	ram[0x40] = 3
 
 	root = RamToTrie(ram)
 	fmt.Println("root(0,4,0x40) =", root)

test/mips_test_memory.js

@@ -22,14 +22,21 @@ describe("MIPSMemory contract", function () {
     let root = "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421"
 
     root = await write(mm, root, 0, 1)
-    root = await write(mm, root, 4, 1)
+    root = await write(mm, root, 4, 2)
+
+    expect(await mm.ReadMemory(root, 0)).to.equal(1)
+    expect(await mm.ReadMemory(root, 4)).to.equal(2)
   })
   it("write three should work", async function() {
     await mm.AddTrieNode(new Uint8Array([0x80]))
     let root = "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421"
 
     root = await write(mm, root, 0, 1)
-    root = await write(mm, root, 4, 1)
-    root = await write(mm, root, 0x40, 1)
+    root = await write(mm, root, 4, 2)
+    root = await write(mm, root, 0x40, 3)
+
+    expect(await mm.ReadMemory(root, 0)).to.equal(1)
+    expect(await mm.ReadMemory(root, 4)).to.equal(2)
+    expect(await mm.ReadMemory(root, 0x40)).to.equal(3)
   })
 })