sglang/test/registered/unit

Unit Tests

CPU-only component tests that do not launch a server, load model weights, or require an accelerator. GPU operator correctness belongs under test/registered/kernels/ops/<group>/.

Quick Start

1. Find the source file under python/sglang/srt/.
2. Create the corresponding test here, mirroring the source tree:

   srt/mem_cache/radix_cache.py       →  unit/mem_cache/test_radix_cache.py
   srt/sampling/sampling_params.py    →  unit/sampling/test_sampling_params.py
   

3. Register for CI at the top of the file (after imports, before test classes):

   from sglang.test.ci.ci_register import register_cpu_ci
   register_cpu_ci(est_time=5, suite="base-a-test-cpu")
   

4. Run locally:

   pytest test/registered/unit/ -v            # all unit tests
   pytest test/registered/unit/mem_cache/ -v  # one module
   

5. Run with coverage:

   # summary
   pytest test/registered/unit/ --cov --cov-config=.coveragerc -v
   
   # PR incremental check (require ≥60% on changed lines)
   pytest test/registered/unit/ --cov --cov-config=.coveragerc --cov-report=xml
   diff-cover coverage.xml --compare-branch=origin/main --fail-under=60
   

Examples

Basic unit test

"""Unit tests for <module> — no server, no model loading."""

from sglang.test.ci.ci_register import register_cpu_ci

register_cpu_ci(est_time=5, suite="base-a-test-cpu")

import unittest

from sglang.srt.<module> import TargetClass
from sglang.test.test_utils import CustomTestCase


class TestTargetClass(CustomTestCase):
    def test_basic_behavior(self):
        obj = TargetClass(...)
        self.assertEqual(obj.method(), expected)


if __name__ == "__main__":
    unittest.main()

Stubbing GPU-only imports for CPU tests

Some modules (e.g. scheduler.py, io_struct.py) transitively import packages like sgl_kernel that require a GPU to initialize. To run pure-mock tests against these modules on CPU-only CI, stub the problematic package before importing it.

maybe_stub_sgl_kernel() in test_utils.py does this for sgl_kernel: it's a no-op on GPU machines, and on CPU it installs a sys.meta_path finder that auto-creates empty stub modules for all sgl_kernel.* submodules.

from sglang.test.ci.ci_register import register_cpu_ci
from sglang.test.test_utils import maybe_stub_sgl_kernel

maybe_stub_sgl_kernel()  # must precede any import that pulls in sgl_kernel

from sglang.srt.managers.io_struct import FlushCacheReqInput
from sglang.srt.managers.scheduler import Scheduler

register_cpu_ci(est_time=2, suite="base-a-test-cpu")

The same pattern (sys.meta_path finder) can be applied to other GPU-only packages. See maybe_stub_sgl_kernel() in python/sglang/test/test_utils.py for the implementation. Do not directly mutate sys.modules at module level — pytest imports all test files before running any, so such mutations pollute the entire process. If you must stub, use patch.dict("sys.modules", ...) with proper cleanup.

Rules

• No popen_launch_server() or Engine(...).
• No model weight loading.
• Use CustomTestCase (from sglang.test.test_utils, adds CI retry).
• Mock external or slow dependency boundaries only when the assertion still checks a result, state transition, protocol output, or error. A test that proves only that its mock was called is not sufficient.