[cdc_rsync] Add integration tests (#42)

[cdc_rsync] Add integration tests

This CL adds Python integration tests for cdc_rsync. To run the tests,
you need to supply a Linux host and proper configuration for cdc_rsync
to work:

  set CDC_SSH_COMMAND=C:\path\to\ssh.exe <args>
  set CDC_SCP_COMMAND=C:\path\to\scp.exe <args>
  C:\python38\python.exe -m integration_tests.cdc_rsync.all_tests --binary_path=C:\full\path\to\cdc_rsync.exe --user_host=user@host

Ran the tests and made sure they worked.

integration_tests/framework/test_base.py

@@ -0,0 +1,63 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Lint as: python3
+"""Test main and flags."""
+
+import argparse
+import contextlib
+import logging
+import sys
+import unittest
+
+from integration_tests.framework import test_runner
+
+
+class Flags(object):
+  binary_path = None
+  user_host = None
+  ssh_port = 22
+
+
+def main():
+  parser = argparse.ArgumentParser(description='End-to-end integration test.')
+  parser.add_argument('--binary_path', help='Target [user@]host', required=True)
+  parser.add_argument('--user_host', help='Target [user@]host', required=True)
+  parser.add_argument(
+      '--ssh_port',
+      type=int,
+      help='SSH port for connecting to the host',
+      default=22)
+  parser.add_argument('--log_file', help='Log file path')
+
+  # Capture all remaining arguments to pass to unittest.main().
+  args, unittest_args = parser.parse_known_args()
+  Flags.binary_path = args.binary_path
+  Flags.user_host = args.user_host
+  Flags.ssh_port = args.ssh_port
+
+  # Log to STDERR
+  log_format = ('%(levelname)-8s%(asctime)s '
+                '%(filename)s:%(lineno)-3d %(message)s')
+  log_stream = sys.stderr
+
+  if args.log_file:
+    log_stream = open(args.log_file, 'w')
+
+  with log_stream:
+    logging.basicConfig(
+        format=log_format, level=logging.DEBUG, stream=log_stream)
+
+    unittest.main(
+        argv=sys.argv[:1] + unittest_args, testRunner=test_runner.TestRunner())