feat: Add .yml to watched file extensions and add unit tests for AgentChangeEventHandler

Close #3834

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 843409166

Author: GWeale

src/google/adk/cli/utils/agent_change_handler.py

@@ -38,7 +38,7 @@ def __init__(
     self.current_app_name_ref = current_app_name_ref
 
   def on_modified(self, event):
-    if not (event.src_path.endswith(".py") or event.src_path.endswith(".yaml")):
+    if not event.src_path.endswith((".py", ".yaml", ".yml")):
       return
     logger.info("Change detected in agents directory: %s", event.src_path)
     self.agent_loader.remove_agent_from_cache(self.current_app_name_ref.value)

tests/unittests/cli/utils/test_agent_change_handler.py

@@ -0,0 +1,91 @@
+# Copyright 2025 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.
+
+from unittest import mock
+
+from google.adk.cli.utils import agent_loader
+from google.adk.cli.utils.agent_change_handler import AgentChangeEventHandler
+from google.adk.cli.utils.shared_value import SharedValue
+import pytest
+from watchdog.events import FileModifiedEvent
+
+
+class TestAgentChangeEventHandler:
+  """Unit tests for AgentChangeEventHandler file extension filtering."""
+
+  @pytest.fixture
+  def mock_agent_loader(self):
+    """Create a mock AgentLoader constrained to the public API."""
+    return mock.create_autospec(
+        agent_loader.AgentLoader, instance=True, spec_set=True
+    )
+
+  @pytest.fixture
+  def handler(self, mock_agent_loader):
+    """Create an AgentChangeEventHandler with mocked dependencies."""
+    runners_to_clean = set()
+    current_app_name_ref = SharedValue(value="test_agent")
+    return AgentChangeEventHandler(
+        agent_loader=mock_agent_loader,
+        runners_to_clean=runners_to_clean,
+        current_app_name_ref=current_app_name_ref,
+    )
+
+  @pytest.mark.parametrize(
+      "file_path",
+      [
+          pytest.param("/path/to/agent.py", id="python_file"),
+          pytest.param("/path/to/config.yaml", id="yaml_file"),
+          pytest.param("/path/to/config.yml", id="yml_file"),
+      ],
+  )
+  def test_on_modified_triggers_reload_for_supported_extensions(
+      self, handler, mock_agent_loader, file_path
+  ):
+    """Verify that .py, .yaml, and .yml files trigger agent reload."""
+    event = FileModifiedEvent(src_path=file_path)
+
+    handler.on_modified(event)
+
+    mock_agent_loader.remove_agent_from_cache.assert_called_once_with(
+        "test_agent"
+    )
+    assert (
+        "test_agent" in handler.runners_to_clean
+    ), f"Expected 'test_agent' in runners_to_clean for {file_path}"
+
+  @pytest.mark.parametrize(
+      "file_path",
+      [
+          pytest.param("/path/to/file.json", id="json_file"),
+          pytest.param("/path/to/file.txt", id="txt_file"),
+          pytest.param("/path/to/file.md", id="markdown_file"),
+          pytest.param("/path/to/file.toml", id="toml_file"),
+          pytest.param("/path/to/.gitignore", id="gitignore_file"),
+          pytest.param("/path/to/file", id="no_extension"),
+      ],
+  )
+  def test_on_modified_ignores_unsupported_extensions(
+      self, handler, mock_agent_loader, file_path
+  ):
+    """Verify that non-py/yaml/yml files do not trigger reload."""
+    event = FileModifiedEvent(src_path=file_path)
+
+    handler.on_modified(event)
+
+    mock_agent_loader.remove_agent_from_cache.assert_not_called()
+    assert not handler.runners_to_clean, (
+        f"Expected runners_to_clean to be empty for {file_path}, "
+        f"got {handler.runners_to_clean}"
+    )