ci: add tear down for openthread ci case

examples/openthread/pytest_otbr.py

@@ -10,6 +10,7 @@ import secrets
 import subprocess
 import threading
 import time
+from typing import Generator
 from typing import Optional
 from typing import Tuple
 
@@ -86,6 +87,25 @@ ESPPORT3 = os.getenv('ESPPORT3')
 PORT_MAPPING = {'ESPPORT1': 'esp32h2', 'ESPPORT2': 'esp32s3', 'ESPPORT3': 'esp32c6'}
 
 
+@pytest.fixture(scope='module', autouse=True)
+def erase_flash_after_all_cases() -> Generator[None, None, None]:
+    yield
+
+    serial_ports = list(dict.fromkeys(filter(None, map(os.getenv, PORT_MAPPING))))
+    failed_ports = []
+    for serial_port in serial_ports:
+        command = ['python', '-m', 'esptool', '--port', serial_port, 'erase_flash']
+        logging.info('Erasing flash on %s: %s', serial_port, ' '.join(command))
+        result = subprocess.run(command, capture_output=True, text=True)
+        logging.info('Erase flash stdout on %s:\n%s', serial_port, result.stdout)
+        if result.stderr:
+            logging.info('Erase flash stderr on %s:\n%s', serial_port, result.stderr)
+        if result.returncode != 0:
+            failed_ports.append(serial_port)
+
+    assert not failed_ports, f'Failed to erase flash on ports: {failed_ports}'
+
+
 # Case 1: Thread network formation and attaching
 @pytest.mark.openthread_br
 @pytest.mark.flaky(reruns=1, reruns_delay=5)