testrunner/utils: add helper for test_utils_interactive_sync

Add helper to do the synchronisation.

dist/pythonlibs/testrunner/__init__.py

@@ -14,6 +14,7 @@ import pexpect
 
 from .spawn import find_exc_origin, setup_child, teardown_child
 from .unittest import PexpectTestCase   # noqa, F401 expose to users
+from .utils import test_utils_interactive_sync # noqa, F401 expose to users
 
 # Timeout for tests can be changed by setting RIOT_TEST_TIMEOUT to the desired
 # value in the environment variables

dist/pythonlibs/testrunner/utils.py

@@ -0,0 +1,27 @@
+# Copyright (C) 2019 Freie Universität Berlin
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+"""Utility functions for writing tests."""
+
+import pexpect
+
+
+def test_utils_interactive_sync(child, retries=5, delay=1):
+    """Synchronisation for 'test_utils_interactive_sync' function.
+
+    Interacts through input to wait for node being ready.
+    """
+    for _ in range(0, retries):
+        child.sendline('r')
+        ret = child.expect_exact(['READY', pexpect.TIMEOUT], timeout=delay)
+        if ret == 0:
+            break
+    else:
+        # Last call to make it fail her,
+        child.expect_exact('READY', timeout=0)
+
+    child.sendline('s')
+    child.expect_exact('START')