From 1aed39a848e5013f118d9d9600098191080cc0ca Mon Sep 17 00:00:00 2001
From: benedikt-bartscher
 <31854409+benedikt-bartscher@users.noreply.github.com>
Date: Thu, 10 Oct 2024 21:18:57 +0200
Subject: [PATCH] catch ValueError("I/O operation on closed file.") if frontend
 crashes (#4150)

---
 reflex/testing.py | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/reflex/testing.py b/reflex/testing.py
index 7ea524f1c..6a45c51eb 100644
--- a/reflex/testing.py
+++ b/reflex/testing.py
@@ -394,9 +394,14 @@ class AppHarness:
 
         def consume_frontend_output():
             while True:
-                line = (
-                    self.frontend_process.stdout.readline()  # pyright: ignore [reportOptionalMemberAccess]
-                )
+                try:
+                    line = (
+                        self.frontend_process.stdout.readline()  # pyright: ignore [reportOptionalMemberAccess]
+                    )
+                # catch I/O operation on closed file.
+                except ValueError as e:
+                    print(e)
+                    break
                 if not line:
                     break
                 print(line)