test: fix test_tool_choice (#1234)

Summary:

Test Plan:
---
[//]: # (BEGIN SAPLING FOOTER)
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* __->__ #1234
* #1214

tests/client-sdk/agents/test_agents.py

@@ -325,20 +325,16 @@ def test_custom_tool(llama_stack_client, agent_config):
 
 
 def test_tool_choice(llama_stack_client, agent_config):
-    data = [
-        ("required", '{"type": "function"'),
-        ("none", None),
-        ("get_boiling_point", '{"type": "function", "name": "get_boiling_point"'),
-    ]
-    client_tool = TestClientTool()
-    for tool_choice, expected_tool in data:
-        agent_config = {
+    def run_agent(tool_choice):
+        client_tool = TestClientTool()
+
+        test_agent_config = {
             **agent_config,
             "tool_config": {"tool_choice": tool_choice},
             "client_tools": [client_tool.get_tool_definition()],
         }
 
-        agent = Agent(llama_stack_client, agent_config, client_tools=(client_tool,))
+        agent = Agent(llama_stack_client, test_agent_config, client_tools=(client_tool,))
         session_id = agent.create_session(f"test-session-{uuid4()}")
 
         response = agent.create_turn(
@@ -349,14 +345,19 @@ def test_tool_choice(llama_stack_client, agent_config):
                 },
             ],
             session_id=session_id,
+            stream=False,
         )
 
-        logs = [str(log) for log in EventLogger().log(response) if log is not None]
-        logs_str = "".join(logs)
-        if expected_tool:
-            assert expected_tool in logs_str
-        else:
-            assert '{"type": "function"' not in logs_str
+        return [step for step in response.steps if step.step_type == "tool_execution"]
+
+    tool_execution_steps = run_agent("required")
+    assert len(tool_execution_steps) > 0
+
+    tool_execution_steps = run_agent("none")
+    assert len(tool_execution_steps) == 0
+
+    tool_execution_steps = run_agent("get_boiling_point")
+    assert len(tool_execution_steps) == 1 and tool_execution_steps[0].tool_calls[0].tool_name == "get_boiling_point"
 
 
 # TODO: fix this flaky test