diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 7191b5fd..9c29cc2f 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -35,6 +35,7 @@ jobs:
           - '3.10'
           - '3.11'
           - '3.12'
+          - '3.13'
           - 'pypy-3.9'
           - 'pypy-3.10'
         toxenv: [py]
diff --git a/setup.cfg b/setup.cfg
index d5a3a1a6..318ddd8c 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -30,6 +30,7 @@ classifiers =
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
     Programming Language :: Python :: 3.12
+    Programming Language :: Python :: 3.13
     Programming Language :: Python :: Implementation :: CPython
     Programming Language :: Python :: Implementation :: PyPy
     License :: OSI Approved :: MIT License
diff --git a/test/test_execution.py b/test/test_execution.py
index 871a7d15..2042cdfc 100644
--- a/test/test_execution.py
+++ b/test/test_execution.py
@@ -213,11 +213,22 @@ def runner() -> int:
 
     thread = threading.Thread(target=runner)
     thread.start()
-    sleep(0.3)  # make sure the process is started
-    ps_command = "ps aux | grep '[s]leep 60.74016230000801'"  # brackets to not match grep process
-    ps_output = subprocess.check_output(ps_command, shell=True).decode()
-    pid = int(ps_output.split()[1])
-    os.kill(pid, signal.SIGTERM)
+    retries = 20
+    pid = None
+    for i in range(retries):
+        try:
+            ps_command = "ps auxww | grep '[s]leep 60.74016230000801'"  # brackets to not match grep process
+            ps_output = subprocess.check_output(ps_command, shell=True).decode()
+            pid = int(ps_output.split()[1])
+            break
+        except subprocess.CalledProcessError as e:
+            print(f"Attempt {i} failed with msg: {e}", file=sys.stderr)
+            sleep(0.1)  # Retry after a short delay
+
+    if pid is not None:
+        os.kill(pid, signal.SIGTERM)
+    else:
+        raise RuntimeError("Failed to find sleep process")
 
     thread.join()
     # Cannot retrieve the exit code from the thread, it is written to the file
diff --git a/tox.ini b/tox.ini
index c5e67e31..4868b96c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = lint,typing,py38,py39,py310,py311,py312,pypy3
+envlist = lint,typing,py39,py310,py311,py312,py313,pypy3
 skip_missing_interpreters = True
 isolated_build = True
 minversion = 3.3.0