scripts: tests: twister: Add log_helper tests

Log helper is a small module that this commit
covers with an explicit test.

Signed-off-by: Lukasz Mrugala <lukaszx.mrugala@intel.com>

scripts/tests/twister/test_log_helper.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+# Copyright (c) 2023 Intel Corporation
+#
+# SPDX-License-Identifier: Apache-2.0
+"""
+Tests for log_helper.py functions
+"""
+
+import logging
+import mock
+import pytest
+
+from importlib import reload
+
+import twisterlib.log_helper
+
+
+TESTDATA = [
+    ('Windows', 'dummy message: [\'dummy\', \'command\', \'-flag\']'),
+    ('Linux', 'dummy message: dummy command -flag'),
+]
+
+@pytest.mark.parametrize(
+    'system, expected_log',
+    TESTDATA,
+    ids=['Windows', 'Linux']
+)
+def test_log_command(caplog, system, expected_log):
+    caplog.set_level(logging.DEBUG)
+
+    logger = logging.getLogger('dummy')
+    message = 'dummy message'
+    args = ['dummy', 'command', '-flag']
+
+    with mock.patch('platform.system', return_value=system):
+        reload(twisterlib.log_helper)
+        twisterlib.log_helper.log_command(logger, message, args)
+
+    reload(twisterlib.log_helper)
+
+    assert expected_log in caplog.text