[Refactor] Consolidate GPT-OSS reasoning parser tests (#36915)

Signed-off-by: sfeng33 <4florafeng@gmail.com>
Signed-off-by: Flora Feng <4florafeng@gmail.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

tests/reasoning/test_gptoss_reasoning_parser.py

@@ -1,11 +1,19 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
+import json
+from unittest.mock import Mock
+
 import pytest
 from transformers import AutoTokenizer
 
+from vllm.entrypoints.mcp.tool_server import ToolServer
 from vllm.reasoning import ReasoningParser
-from vllm.reasoning.gptoss_reasoning_parser import GptOssReasoningParser
+from vllm.reasoning.gptoss_reasoning_parser import (
+    GptOssReasoningParser,
+    from_builtin_tool_to_tag,
+    no_func_reasoning_tag,
+)
 
 REASONING_MODEL_NAME = "openai/gpt-oss-120b"
 
@@ -142,3 +150,133 @@ def test_gptoss_is_reasoning_end(
     output_ids = gpt_oss_tokenizer.convert_tokens_to_ids(output)
     actual_is_reasoning_end = parser.is_reasoning_end(output_ids)
     assert is_reasoning_end == actual_is_reasoning_end
+
+
+class TestGptOssStructuralTags:
+    """Test cases for GptOssReasoningParser structural tag functionality."""
+
+    @pytest.fixture
+    def mock_tokenizer(self):
+        """Create a mock tokenizer for testing."""
+        tokenizer = Mock()
+        tokenizer.encode = Mock(return_value=[1, 2, 3, 4, 5])
+        tokenizer.get_vocab = Mock(return_value={"<|end|>": 6})
+        return tokenizer
+
+    @pytest.fixture
+    def reasoning_parser(self, mock_tokenizer):
+        """Create a GptOssReasoningParser instance."""
+        return GptOssReasoningParser(mock_tokenizer)
+
+    def test_prepare_structured_tag_no_tool_server(self, reasoning_parser):
+        """Test prepare_structured_tag with no tool server."""
+        result = reasoning_parser.prepare_structured_tag(None, None)
+        expected = json.dumps(no_func_reasoning_tag)
+
+        assert result == expected
+
+        # Verify the structure is correct
+        parsed = json.loads(result)
+        assert parsed["type"] == "structural_tag"
+        assert parsed["format"]["type"] == "triggered_tags"
+        assert len(parsed["format"]["tags"]) == 1
+        assert parsed["format"]["tags"][0]["begin"] == "<|channel|>analysis<|message|>"
+        assert parsed["format"]["triggers"] == ["<|channel|>analysis"]
+
+    def test_prepare_structured_tag_with_original_tag(self, reasoning_parser):
+        """Test prepare_structured_tag when original_tag is provided."""
+        original_tag = '{"custom": "tag"}'
+        result = reasoning_parser.prepare_structured_tag(original_tag, None)
+
+        # Should return the original tag unchanged
+        assert result == original_tag
+
+    def test_from_builtin_tool_to_tag(self):
+        """Test from_builtin_tool_to_tag function."""
+        tags = from_builtin_tool_to_tag("python")
+
+        assert len(tags) == 2
+        assert tags[0]["begin"] == "<|channel|>commentary to=python"
+        assert tags[0]["content"]["type"] == "any_text"
+        assert tags[0]["end"] == "<|end|>"
+
+        assert tags[1]["begin"] == "<|channel|>analysis to=python"
+        assert tags[1]["content"]["type"] == "any_text"
+        assert tags[1]["end"] == "<|end|>"
+
+    @pytest.mark.parametrize(
+        "tools",
+        [
+            [],
+            ["browser"],
+            ["python"],
+            ["container"],
+            ["browser", "python"],
+            ["browser", "container"],
+            ["python", "container"],
+            ["browser", "python", "container"],
+        ],
+    )
+    def test_json_validity_comprehensive(self, reasoning_parser, tools):
+        """Test JSON validity across all possible tool combinations."""
+        tool_server = Mock(spec=ToolServer)
+        tool_server.has_tool = Mock(side_effect=lambda tool: tool in tools)
+
+        result = reasoning_parser.prepare_structured_tag(None, tool_server)
+        parsed_result = json.loads(result)
+
+        assert parsed_result["type"] == "structural_tag"
+        assert "format" in parsed_result
+        assert "tags" in parsed_result["format"]
+        assert "triggers" in parsed_result["format"]
+
+        # Tag count should be: 1 (analysis) + 2 * len(tools)
+        expected_tag_count = 1 + (2 * len(tools))
+        assert len(parsed_result["format"]["tags"]) == expected_tag_count
+
+        # Verify triggers are correctly configured
+        expected_triggers = ["<|channel|>analysis"]
+        if tools:
+            expected_triggers.append("<|channel|>commentary to=")
+        assert set(parsed_result["format"]["triggers"]) == set(expected_triggers)
+
+    def test_no_cross_request_state_pollution(self, reasoning_parser):
+        """Test that sequential calls with different tool servers produce
+        independent results, guarding against shared mutable state
+        (e.g. missing deepcopy in tag_with_builtin_funcs)."""
+        tool_server_1 = Mock(spec=ToolServer)
+        tool_server_1.has_tool = Mock(side_effect=lambda tool: tool == "python")
+
+        tool_server_2 = Mock(spec=ToolServer)
+        tool_server_2.has_tool = Mock(side_effect=lambda tool: tool == "browser")
+
+        result_1 = reasoning_parser.prepare_structured_tag(None, tool_server_1)
+        result_2 = reasoning_parser.prepare_structured_tag(None, tool_server_2)
+
+        tags_1 = [tag["begin"] for tag in json.loads(result_1)["format"]["tags"]]
+        tags_2 = [tag["begin"] for tag in json.loads(result_2)["format"]["tags"]]
+
+        assert "<|channel|>commentary to=python" in tags_1
+        assert "<|channel|>commentary to=browser" not in tags_1
+
+        assert "<|channel|>commentary to=browser" in tags_2
+        assert "<|channel|>commentary to=python" not in tags_2
+
+    def test_tag_format_consistency(self, reasoning_parser):
+        """Test that all generated tags follow consistent format,
+        catching malformed tags from from_builtin_tool_to_tag."""
+        tool_server = Mock(spec=ToolServer)
+        tool_server.has_tool = Mock(
+            side_effect=lambda tool: tool in ["python", "browser"]
+        )
+
+        result = reasoning_parser.prepare_structured_tag(None, tool_server)
+        parsed_result = json.loads(result)
+
+        for tag in parsed_result["format"]["tags"]:
+            assert "begin" in tag
+            assert "content" in tag
+            assert "end" in tag
+            assert tag["content"]["type"] == "any_text"
+            assert tag["end"] == "<|end|>"
+            assert tag["begin"].startswith("<|channel|>")