From c2c87e4ad11387c8ffa7ea511ef24c649199416d Mon Sep 17 00:00:00 2001
From: 0x0v4 <20mitchellthomas02@gmail.com>
Date: Thu, 26 Feb 2026 09:01:51 +0100
Subject: [PATCH] Fix invalid negative index usage when mutating last byte

The tests used new_data[-1] to mutate the last byte of account data. In JavaScript/TypeScript, negative indices are not valid array indices.
new_data[-1] evaluates to undefined, resulting in NaN, and creates a "-1" object property instead of modifying the last byte.

As a result, the account data was not actually modified, and the commit tests were not validating real state changes.

Replaced negative index usage with explicit last-index access:
```ts
const lastIndex = new_data.length - 1;
new_data[lastIndex] = (new_data[lastIndex] + 1) % 256;
```
Applied this fix in both Commit a new state to the PDA test cases.

This:
- Ensures the last byte of the buffer is actually mutated
- Makes state changes explicit
- Keeps changes minimal
- Preserves existing test structure and logic

This restores correct state mutation semantics and ensures the commit tests validate real data changes.

Additionally, changed let to const for account and new_data since they are not reassigned.
---
 tests/integration/tests/test-delegation.ts | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/tests/integration/tests/test-delegation.ts b/tests/integration/tests/test-delegation.ts
index cf7a7e19..210e1116 100644
--- a/tests/integration/tests/test-delegation.ts
+++ b/tests/integration/tests/test-delegation.ts
@@ -208,9 +208,11 @@ describe("TestDelegation", () => {
   });
 
   it("Commit a new state to the PDA", async () => {
-    let account = await provider.connection.getAccountInfo(pda);
-    let new_data = account.data;
-    new_data[-1] = (new_data[-1] + 1) % 256;
+    const account = await provider.connection.getAccountInfo(pda);
+    const new_data = account.data;
+
+    const lastIndex = new_data.length - 1;
+    new_data[lastIndex] = (new_data[lastIndex] + 1) % 256;
 
     const args: CommitAccountInstructionArgs = {
       slot: new anchor.BN(1),
@@ -316,9 +318,11 @@ describe("TestDelegation", () => {
   });
 
   it("Commit a new state to the PDA", async () => {
-    let account = await provider.connection.getAccountInfo(pda);
-    let new_data = account.data;
-    new_data[-1] = (new_data[-1] + 1) % 256;
+    const account = await provider.connection.getAccountInfo(pda);
+    const new_data = account.data;
+
+    const lastIndex = new_data.length - 1;
+    new_data[lastIndex] = (new_data[lastIndex] + 1) % 256;
 
     const args: CommitAccountInstructionArgs = {
       slot: new anchor.BN(2),