From e51cfc2b93de245dd7a54d05445fd9eab6644a81 Mon Sep 17 00:00:00 2001
From: Mischa Untaga <99098079+MischaU8@users.noreply.github.com>
Date: Tue, 16 Jan 2024 11:59:07 +0100
Subject: detect when undo causes random seed change

---
 rtt-module.js | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/rtt-module.js b/rtt-module.js
index c0bc30f..5fe60ba 100755
--- a/rtt-module.js
+++ b/rtt-module.js
@@ -118,6 +118,7 @@ module.exports.fuzz = function(fuzzerInputData) {
 
         let action = data.pickValue(Object.keys(actions))
         let args = actions[action]
+        let seed = state.seed
 
         if (args !== undefined && args !== null && typeof args !== "number" && typeof args !== "boolean") {
             // check for NaN as any suggested action argument and raise an error on those
@@ -138,9 +139,15 @@ module.exports.fuzz = function(fuzzerInputData) {
             throw new RulesCrashError(e, e.stack)
         }
 
-        if (action === "undo" && state.active !== active) {
-            log_crash(replay, state, view, step, active)
-            throw new UndoActiveError(`undo caused active to switch from ${active} to ${state.active}`)
+        if (action === "undo") {
+            if (state.active !== active) {
+                log_crash(replay, state, view, step, active)
+                throw new UndoActiveError(`undo caused active to switch from ${active} to ${state.active}`)
+            }
+            if (state.seed !== seed) {
+                log_crash(replay, state, view, step, active)
+                throw new UndoSeedError(`undo caused seed change from ${seed} to ${state.seed}`)
+            }
         }
         step += 1
     }
@@ -198,6 +205,13 @@ class UndoActiveError extends Error {
     }
 }
 
+class UndoSeedError extends Error {
+    constructor(message) {
+      super(message)
+      this.name = "UndoSeedError"
+    }
+}
+
 class RulesCrashError extends Error {
     constructor(message, stack) {
       super(message)
-- 
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