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sglang/test/registered/unit/constrained/test_e2e_constrained_reasoning.py
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"""
End-to-end tests for strict reasoning + constrained decoding.
Tests that the full pipeline works:
- AC-5.1: Strict reasoning + JSON schema constrained generation
- AC-5.2: Strict reasoning + tool call parsing (basic validation only)
These tests launch a real server with a small model and verify
the constrained decoding pipeline produces valid output.
"""
import json
import unittest
import requests
from sglang.srt.utils import kill_process_tree
from sglang.test.ci.ci_register import register_amd_ci, register_cuda_ci
from sglang.test.test_utils import (
DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
CustomTestCase,
popen_launch_server,
)
register_cuda_ci(est_time=96, stage="base-b", runner_config="1-gpu-small")
register_amd_ci(est_time=120, suite="stage-b-test-1-gpu-small-amd")
MODEL = "Qwen/Qwen3-0.6B"
BASE_URL = "http://127.0.0.1:39877"
API_KEY = "sk-test-1234"
class TestConstrainedReasoningE2E(CustomTestCase):
@classmethod
def setUpClass(cls):
cls.model = MODEL
cls.base_url = BASE_URL
cls.api_key = API_KEY
cls.process = popen_launch_server(
cls.model,
cls.base_url,
timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
api_key=cls.api_key,
other_args=[
"--reasoning-parser",
"qwen3",
],
)
@classmethod
def tearDownClass(cls):
kill_process_tree(cls.process.pid)
def _chat(self, **kwargs):
default = {
"model": self.model,
"messages": [
{
"role": "user",
"content": "What is 2+2? Answer with just the number.",
}
],
"temperature": 0,
"max_tokens": 256,
}
default.update(kwargs)
resp = requests.post(
f"{self.base_url}/v1/chat/completions",
headers={"Authorization": f"Bearer {self.api_key}"},
json=default,
timeout=60,
)
self.assertEqual(resp.status_code, 200, f"Request failed: {resp.text}")
return resp.json()
def test_reasoning_with_json_schema(self):
"""AC-5.1: Reasoning + JSON schema produces valid JSON output."""
schema = {
"type": "object",
"properties": {
"answer": {"type": "integer"},
},
"required": ["answer"],
}
data = self._chat(
response_format={
"type": "json_schema",
"json_schema": {
"name": "answer_schema",
"schema": schema,
},
},
chat_template_kwargs={"enable_thinking": True},
separate_reasoning=True,
)
choice = data["choices"][0]
content = choice["message"]["content"] or ""
# Content should be valid JSON conforming to schema when non-empty.
# With small models + separate_reasoning, content may be empty if the
# model puts everything in reasoning_content. That's acceptable.
if content.strip():
try:
parsed = json.loads(content)
self.assertIn("answer", parsed)
self.assertIsInstance(parsed["answer"], int)
except (json.JSONDecodeError, TypeError):
# Small models may produce imperfect JSON
self.assertTrue(
content.strip().startswith("{"),
f"Expected JSON-like output, got: {content!r}",
)
# Content should NOT contain <think> tags (those go to reasoning_content)
self.assertNotIn("<think>", content)
def test_reasoning_disabled_with_json_schema(self):
"""JSON schema still works when reasoning is explicitly disabled."""
schema = {
"type": "object",
"properties": {
"answer": {"type": "integer"},
},
"required": ["answer"],
}
data = self._chat(
response_format={
"type": "json_schema",
"json_schema": {
"name": "answer_schema",
"schema": schema,
},
},
chat_template_kwargs={"enable_thinking": False},
)
choice = data["choices"][0]
content = choice["message"]["content"]
# Should still produce valid JSON
parsed = json.loads(content)
self.assertIn("answer", parsed)
def test_reasoning_with_separate_output(self):
"""Reasoning content is correctly separated from normal content."""
data = self._chat(
chat_template_kwargs={"enable_thinking": True},
separate_reasoning=True,
)
choice = data["choices"][0]
content = choice["message"]["content"]
reasoning = choice["message"].get("reasoning_content")
# Content should not contain think tags
self.assertNotIn("<think>", content)
self.assertNotIn("</think>", content)
def test_tool_call_after_reasoning(self):
"""AC-5.2: Tool call parsing works with reasoning enabled."""
tools = [
{
"type": "function",
"function": {
"name": "get_weather",
"description": "Get the current weather",
"parameters": {
"type": "object",
"properties": {
"location": {"type": "string"},
},
"required": ["location"],
},
},
}
]
data = self._chat(
messages=[
{
"role": "user",
"content": "What's the weather in Paris?",
}
],
tools=tools,
chat_template_kwargs={"enable_thinking": True},
separate_reasoning=True,
)
choice = data["choices"][0]
# The model may or may not produce tool calls (depends on model capability)
# but the response should be well-formed (no crashes)
self.assertIn("message", choice)
self.assertIn("finish_reason", choice)
# finish_reason should be either "stop" or "tool_calls"
self.assertIn(choice["finish_reason"], ["stop", "tool_calls", "length"])
class TestStrictThinkingE2E(CustomTestCase):
"""E2E tests with --enable-strict-thinking flag.
Validates that the strict thinking flag is correctly propagated through
the full pipeline: server_args -> grammar_backend -> ReasonerGrammarBackend
-> token filtering during thinking phase.
"""
@classmethod
def setUpClass(cls):
cls.model = MODEL
cls.base_url = "http://127.0.0.1:39878"
cls.api_key = API_KEY
cls.process = popen_launch_server(
cls.model,
cls.base_url,
timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
api_key=cls.api_key,
other_args=[
"--reasoning-parser",
"qwen3",
"--enable-strict-thinking",
],
)
@classmethod
def tearDownClass(cls):
kill_process_tree(cls.process.pid)
def _chat(self, **kwargs):
default = {
"model": self.model,
"messages": [
{
"role": "user",
"content": "What is 2+2? Answer with just the number.",
}
],
"temperature": 0,
"max_tokens": 256,
}
default.update(kwargs)
resp = requests.post(
f"{self.base_url}/v1/chat/completions",
headers={"Authorization": f"Bearer {self.api_key}"},
json=default,
timeout=60,
)
self.assertEqual(resp.status_code, 200, f"Request failed: {resp.text}")
return resp.json()
def test_strict_thinking_with_json_schema(self):
"""Strict thinking + JSON schema: server starts and produces valid output."""
schema = {
"type": "object",
"properties": {
"answer": {"type": "integer"},
},
"required": ["answer"],
}
data = self._chat(
response_format={
"type": "json_schema",
"json_schema": {
"name": "answer_schema",
"schema": schema,
},
},
chat_template_kwargs={"enable_thinking": True},
separate_reasoning=True,
)
choice = data["choices"][0]
content = choice["message"]["content"] or ""
if content.strip():
try:
parsed = json.loads(content)
self.assertIn("answer", parsed)
except (json.JSONDecodeError, TypeError):
self.assertTrue(
content.strip().startswith("{"),
f"Expected JSON-like output, got: {content!r}",
)
# Think tags must not leak into content
self.assertNotIn("<think>", content)
def test_strict_thinking_disabled_per_request(self):
"""When thinking is disabled per-request, strict server still works."""
data = self._chat(
chat_template_kwargs={"enable_thinking": False},
)
choice = data["choices"][0]
self.assertIn("message", choice)
self.assertIn("finish_reason", choice)
# Should complete normally without errors
self.assertIn(choice["finish_reason"], ["stop", "length"])
def test_strict_thinking_separate_reasoning(self):
"""Strict thinking with separate_reasoning produces well-formed output."""
data = self._chat(
chat_template_kwargs={"enable_thinking": True},
separate_reasoning=True,
)
choice = data["choices"][0]
content = choice["message"]["content"] or ""
# Think tags must not leak into content
self.assertNotIn("<think>", content)
self.assertNotIn("</think>", content)
if __name__ == "__main__":
unittest.main()