[PSM Interop] Add unittests CI with github actions (#34125)

- Add Github Action to conditionally run PSM Interop unit tests:
- Only run when changes are detected in
`tools/run_tests/xds_k8s_test_driver` or any of the proto files used by
the driver
  - Only run against PRs and pushes to `master`, `v1.*.*` branches
  - Runs using `python3.9` and `python3.10`
  - Ready to be added to the list of required GitHub checks
- Add `tools/run_tests/xds_k8s_test_driver/tests/unit/__main__.py` test
loader that recursively discovers all unit tests in
`tools/run_tests/xds_k8s_test_driver/tests/unit`
- Add basic coverage for `XdsTestClient` and `XdsTestServer` to verify
the test loader picks up all folders

Related:
- First unit tests without automated CI added in #34097

.github/workflows/psm-interop.yaml

@@ -0,0 +1,74 @@
+name: PSM Interop
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - 'v1.*'
+
+permissions:
+  contents: read
+
+jobs:
+  unittest:
+    # By default, only version is printed out in parens, e.g. "unittest (3.10)"
+    # This changes it to "unittest (python3.10)"
+    name: "unittest (python${{ matrix.python_version }})"
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python_version: ["3.9", "3.10"]
+      fail-fast: false
+    permissions:
+      pull-requests: read  # Used by paths-filter to read the diff.
+    defaults:
+      run:
+        working-directory: 'tools/run_tests/xds_k8s_test_driver'
+
+    steps:
+      - uses: actions/checkout@v3
+
+      # To add this job to required GitHub checks, it's not enough to use
+      # the on.pull_request.paths filter. For required checks, the job needs to
+      # return the success status, and not be skipped.
+      # Using paths-filter action, we skip the setup/test steps when psm interop
+      # files are unchanged, and the job returns success.
+      - uses: dorny/paths-filter@v2
+        id: paths_filter
+        with:
+          filters:  |
+            psm_interop_src:
+              - 'tools/run_tests/xds_k8s_test_driver/**'
+              - 'src/proto/grpc/testing/empty.proto'
+              - 'src/proto/grpc/testing/messages.proto'
+              - 'src/proto/grpc/testing/test.proto'
+
+      - uses: actions/setup-python@v4
+        if: ${{ steps.paths_filter.outputs.psm_interop_src == 'true' }}
+        with:
+          python-version: "${{ matrix.python_version }}"
+          cache: 'pip'
+          cache-dependency-path: 'tools/run_tests/xds_k8s_test_driver/requirements.lock'
+
+      - name: "Install requirements"
+        if: ${{ steps.paths_filter.outputs.psm_interop_src == 'true' }}
+        run: |
+          pip list
+          pip install --upgrade pip setuptools
+          pip list
+          pip install -r requirements.lock
+          pip list
+
+      - name: "Generate protos"
+        if: ${{ steps.paths_filter.outputs.psm_interop_src == 'true' }}
+        run: >
+          python -m grpc_tools.protoc --proto_path=../../../
+          --python_out=. --grpc_python_out=.
+          src/proto/grpc/testing/empty.proto
+          src/proto/grpc/testing/messages.proto
+          src/proto/grpc/testing/test.proto
+
+      - name: "Run unit tests"
+        if: ${{ steps.paths_filter.outputs.psm_interop_src == 'true' }}
+        run: python -m tests.unit

tools/run_tests/xds_k8s_test_driver/run.sh

@@ -63,5 +63,11 @@ export PYTHONPATH="${XDS_K8S_DRIVER_DIR}"
 # Split path to python file from the rest of the args.
 readonly PY_FILE="$1"
 shift
-# Append args after --flagfile, so they take higher priority.
-exec python "${PY_FILE}" --flagfile="${XDS_K8S_CONFIG}" "$@"
+
+if [[ "${PY_FILE}" =~ tests/unit($|/) ]]; then
+  # Do not set the flagfile when running unit tests.
+  exec python "${PY_FILE}" "$@"
+else
+  # Append args after --flagfile, so they take higher priority.
+  exec python "${PY_FILE}" --flagfile="${XDS_K8S_CONFIG}" "$@"
+fi

tools/run_tests/xds_k8s_test_driver/tests/unit/__main__.py

@@ -0,0 +1,27 @@
+# Copyright 2023 The gRPC Authors
+#
+# 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.
+"""Discover and run all unit tests recursively."""
+
+import pathlib
+
+from absl.testing import absltest
+
+
+def load_tests(loader: absltest.TestLoader, unused_tests, unused_pattern):
+    unit_tests_root = pathlib.Path(__file__).parent
+    return loader.discover(f"{unit_tests_root}", pattern="*_test.py")
+
+
+if __name__ == "__main__":
+    absltest.main()

tools/run_tests/xds_k8s_test_driver/tests/unit/test_app/__init__.py

@@ -0,0 +1,13 @@
+# Copyright 2023 gRPC authors.
+#
+# 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.

tools/run_tests/xds_k8s_test_driver/tests/unit/test_app/client_app_test.py

@@ -0,0 +1,55 @@
+# Copyright 2023 gRPC authors.
+#
+# 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.
+from typing import Optional
+
+from absl.testing import absltest
+
+from framework.test_app import client_app
+
+# Alias
+XdsTestClient = client_app.XdsTestClient
+
+# Test values.
+CANNED_IP: str = "10.0.0.42"
+CANNED_RPC_PORT: int = 1111
+CANNED_HOSTNAME: str = "test-client.local"
+CANNED_SERVER_TARGET: str = "xds:///test-server"
+
+
+class ClientAppTest(absltest.TestCase):
+    """Unit test for the ClientApp."""
+
+    def test_constructor(self):
+        xds_client = XdsTestClient(
+            ip=CANNED_IP,
+            rpc_port=CANNED_RPC_PORT,
+            hostname=CANNED_HOSTNAME,
+            server_target=CANNED_SERVER_TARGET,
+        )
+        # Channels list empty.
+        self.assertEmpty(xds_client.channels)
+
+        # Test fields set as is.
+        self.assertEqual(xds_client.ip, CANNED_IP)
+        self.assertEqual(xds_client.rpc_port, CANNED_RPC_PORT)
+        self.assertEqual(xds_client.server_target, CANNED_SERVER_TARGET)
+        self.assertEqual(xds_client.hostname, CANNED_HOSTNAME)
+
+        # Test optional argument defaults.
+        self.assertEqual(xds_client.rpc_host, CANNED_IP)
+        self.assertEqual(xds_client.maintenance_port, CANNED_RPC_PORT)
+
+
+if __name__ == "__main__":
+    absltest.main()

tools/run_tests/xds_k8s_test_driver/tests/unit/test_app/server_app_test.py

@@ -0,0 +1,84 @@
+# Copyright 2023 gRPC authors.
+#
+# 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.
+from typing import Optional
+
+from absl.testing import absltest
+
+from framework.test_app import server_app
+
+# Alias
+XdsTestServer = server_app.XdsTestServer
+
+# Test values.
+CANNED_IP: str = "10.0.0.43"
+CANNED_RPC_PORT: int = 2222
+CANNED_HOSTNAME: str = "test-server.local"
+CANNED_XDS_HOST: str = "xds-test-server"
+CANNED_XDS_PORT: int = 42
+
+
+class ServerAppTest(absltest.TestCase):
+    """Unit test for the XdsTestServer."""
+
+    def test_constructor(self):
+        xds_server = XdsTestServer(
+            ip=CANNED_IP,
+            rpc_port=CANNED_RPC_PORT,
+            hostname=CANNED_HOSTNAME,
+        )
+        # Channels list empty.
+        self.assertEmpty(xds_server.channels)
+
+        # Test fields set as is.
+        self.assertEqual(xds_server.ip, CANNED_IP)
+        self.assertEqual(xds_server.rpc_port, CANNED_RPC_PORT)
+        self.assertEqual(xds_server.hostname, CANNED_HOSTNAME)
+
+        # Test optional argument defaults.
+        self.assertEqual(xds_server.rpc_host, CANNED_IP)
+        self.assertEqual(xds_server.maintenance_port, CANNED_RPC_PORT)
+        self.assertEqual(xds_server.secure_mode, False)
+
+    def test_xds_address(self):
+        """Verifies the behavior of set_xds_address(), xds_address, xds_uri."""
+        xds_server = XdsTestServer(
+            ip=CANNED_IP,
+            rpc_port=CANNED_RPC_PORT,
+            hostname=CANNED_HOSTNAME,
+        )
+        self.assertEqual(xds_server.xds_uri, "", msg="Must be empty when unset")
+
+        xds_server.set_xds_address(CANNED_XDS_HOST, CANNED_XDS_PORT)
+        self.assertEqual(xds_server.xds_uri, "xds:///xds-test-server:42")
+
+        xds_server.set_xds_address(CANNED_XDS_HOST, None)
+        self.assertEqual(
+            xds_server.xds_uri,
+            "xds:///xds-test-server",
+            msg="Must not contain ':port' when the port is not set",
+        )
+
+        xds_server.set_xds_address(None, None)
+        self.assertEqual(xds_server.xds_uri, "", msg="Must be empty when reset")
+
+        xds_server.set_xds_address(None, CANNED_XDS_PORT)
+        self.assertEqual(
+            xds_server.xds_uri,
+            "",
+            msg="Must be empty when only port is set",
+        )
+
+
+if __name__ == "__main__":
+    absltest.main()