fix(tests): use mock GCS client in artifact service tests to avoid real credentials

Copybara import of the project:

--
ade1d98e030a966183f56cb5c9c1b04cf51f5337 by Thiago Neves <thiagohneves@gmail.com>:

fix(tests): use mock GCS client in artifact service tests to avoid real credentials

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becd2925feebf60196129b029a0ab8d490f7b19e by Thiago Neves <thiagohneves@gmail.com>:

test(agents): add unit tests for live_request_queue, readonly_context, and run_config

COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/641 from thiagoneves:feature/increase-test-coverage 0f7a9fc55d97902e190a394f099324fbeb1541af
PiperOrigin-RevId: 756798390

tests/unittests/agents/test_readonly_context.py

@@ -0,0 +1,33 @@
+import pytest
+from unittest.mock import MagicMock
+from types import MappingProxyType
+from google.adk.agents.readonly_context import ReadonlyContext
+
+
+@pytest.fixture
+def mock_invocation_context():
+  mock_context = MagicMock()
+  mock_context.invocation_id = "test-invocation-id"
+  mock_context.agent.name = "test-agent-name"
+  mock_context.session.state = {"key1": "value1", "key2": "value2"}
+
+  return mock_context
+
+
+def test_invocation_id(mock_invocation_context):
+  readonly_context = ReadonlyContext(mock_invocation_context)
+  assert readonly_context.invocation_id == "test-invocation-id"
+
+
+def test_agent_name(mock_invocation_context):
+  readonly_context = ReadonlyContext(mock_invocation_context)
+  assert readonly_context.agent_name == "test-agent-name"
+
+
+def test_state_content(mock_invocation_context):
+  readonly_context = ReadonlyContext(mock_invocation_context)
+  state = readonly_context.state
+
+  assert isinstance(state, MappingProxyType)
+  assert state["key1"] == "value1"
+  assert state["key2"] == "value2"