test(agent_transfer): add regression tests for non-LlmAgent peer transfers

tests/unittests/flows/llm_flows/test_get_transfer_targets.py

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+# 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.
+
+"""Regression tests for _get_transfer_targets in agent_transfer module."""
+
+from __future__ import annotations
+
+from google.adk.agents.llm_agent import Agent
+from google.adk.agents.loop_agent import LoopAgent
+from google.adk.agents.parallel_agent import ParallelAgent
+from google.adk.agents.sequential_agent import SequentialAgent
+from google.adk.flows.llm_flows.agent_transfer import _get_transfer_targets
+
+from ... import testing_utils
+
+
+def test_loop_agent_peer_does_not_raise_attribute_error():
+  """LoopAgent as a peer agent must not raise AttributeError.
+
+  Regression test for https://github.com/google/adk-python/issues/5863.
+  LoopAgent has no 'mode' attribute; _get_transfer_targets must not crash
+  when iterating over peer agents of an LlmAgent.
+  """
+  mock_model = testing_utils.MockModel.create(responses=['response'])
+
+  loop_peer = LoopAgent(name='loop_peer', sub_agents=[])
+  llm_agent = Agent(name='llm_agent', model=mock_model)
+
+  Agent(
+      name='root',
+      model=mock_model,
+      sub_agents=[llm_agent, loop_peer],
+  )
+
+  targets = _get_transfer_targets(llm_agent)
+  target_names = [t.name for t in targets]
+  assert 'loop_peer' in target_names
+
+
+def test_loop_agent_sub_agent_does_not_raise_attribute_error():
+  """LoopAgent as a sub-agent of the current agent must not raise AttributeError.
+
+  Regression test for https://github.com/google/adk-python/issues/5863.
+  """
+  mock_model = testing_utils.MockModel.create(responses=['response'])
+
+  loop_sub = LoopAgent(name='loop_sub', sub_agents=[])
+  llm_agent = Agent(
+      name='llm_agent',
+      model=mock_model,
+      sub_agents=[loop_sub],
+  )
+
+  targets = _get_transfer_targets(llm_agent)
+  target_names = [t.name for t in targets]
+  assert 'loop_sub' in target_names
+
+
+def test_sequential_agent_peer_does_not_raise_attribute_error():
+  """SequentialAgent as a peer agent must not raise AttributeError.
+
+  Regression test for https://github.com/google/adk-python/issues/5863.
+  SequentialAgent has no 'mode' attribute; the hasattr guard must cover it.
+  """
+  mock_model = testing_utils.MockModel.create(responses=['response'])
+
+  seq_peer = SequentialAgent(name='seq_peer', sub_agents=[])
+  llm_agent = Agent(name='llm_agent', model=mock_model)
+
+  Agent(
+      name='root',
+      model=mock_model,
+      sub_agents=[llm_agent, seq_peer],
+  )
+
+  targets = _get_transfer_targets(llm_agent)
+  target_names = [t.name for t in targets]
+  assert 'seq_peer' in target_names
+
+
+def test_parallel_agent_peer_does_not_raise_attribute_error():
+  """ParallelAgent as a peer agent must not raise AttributeError.
+
+  Regression test for https://github.com/google/adk-python/issues/5863.
+  ParallelAgent has no 'mode' attribute; the hasattr guard must cover it.
+  """
+  mock_model = testing_utils.MockModel.create(responses=['response'])
+
+  par_peer = ParallelAgent(name='par_peer', sub_agents=[])
+  llm_agent = Agent(name='llm_agent', model=mock_model)
+
+  Agent(
+      name='root',
+      model=mock_model,
+      sub_agents=[llm_agent, par_peer],
+  )
+
+  targets = _get_transfer_targets(llm_agent)
+  target_names = [t.name for t in targets]
+  assert 'par_peer' in target_names
+
+
+def test_single_turn_peer_is_excluded_from_transfer_targets():
+  """LlmAgent with mode='single_turn' must be excluded from peer targets.
+
+  Verifies the filtering logic: agents in single_turn mode should not be
+  offered as transfer destinations since they are not interactive.
+  """
+  mock_model = testing_utils.MockModel.create(responses=['response'])
+
+  single_turn_peer = Agent(
+      name='single_turn_peer', model=mock_model, mode='single_turn'
+  )
+  llm_agent = Agent(name='llm_agent', model=mock_model)
+
+  Agent(
+      name='root',
+      model=mock_model,
+      sub_agents=[llm_agent, single_turn_peer],
+  )
+
+  targets = _get_transfer_targets(llm_agent)
+  target_names = [t.name for t in targets]
+  assert 'single_turn_peer' not in target_names