chore: import upstream snapshot with attribution

tests/unittests/tools/environment_simulation/test_environment_simulation_plugin.py

@@ -0,0 +1,46 @@
+# Copyright 2026 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.mock import AsyncMock
+from unittest.mock import MagicMock
+from unittest.mock import patch
+
+from google.adk.tools.environment_simulation.environment_simulation_plugin import EnvironmentSimulationPlugin
+import pytest
+
+
+@pytest.mark.asyncio
+class TestEnvironmentSimulationPlugin:
+  """Test cases for the EnvironmentSimulationPlugin."""
+
+  @pytest.fixture
+  def mock_simulator_engine(self):
+    """Fixture for a mock EnvironmentSimulationEngine."""
+    engine = MagicMock()
+    engine.simulate = AsyncMock()
+    return engine
+
+  async def test_before_tool_callback(self, mock_simulator_engine):
+    """Test that the before_tool_callback calls the engine's simulate method."""
+    plugin = EnvironmentSimulationPlugin(mock_simulator_engine)
+
+    mock_tool = MagicMock()
+    mock_args = {}
+    mock_context = MagicMock()
+
+    await plugin.before_tool_callback(mock_tool, mock_args, mock_context)
+
+    mock_simulator_engine.simulate.assert_awaited_once_with(
+        mock_tool, mock_args, mock_context
+    )