Add the KV-canary perturb framework for fault-injection self-tests (#26816)

test/registered/kv_canary/test_self_unit_perturb.py

@@ -0,0 +1,59 @@
+from __future__ import annotations
+
+import os
+import unittest
+from unittest.mock import patch
+
+from sglang.srt.kv_canary.perturb.config import (
+    PerturbConfig,
+    TargetGroupKind,
+    _parse_target_group_kind,
+)
+from sglang.test.ci.ci_register import register_cuda_ci
+from sglang.test.test_utils import CustomTestCase
+
+register_cuda_ci(est_time=10, stage="extra-a", runner_config="1-gpu-small")
+
+
+class TestParseTargetGroupKind(CustomTestCase):
+    def test_parse_target_group_kind_accepts_valid_values_case_insensitively(
+        self,
+    ) -> None:
+        """Verify target group kind parsing accepts valid names case-insensitively."""
+        cases = [
+            ("full", TargetGroupKind.FULL),
+            ("FULL", TargetGroupKind.FULL),
+            (" swa ", TargetGroupKind.SWA),
+        ]
+
+        for raw, expected in cases:
+            with self.subTest(raw=raw):
+                self.assertEqual(_parse_target_group_kind(raw), expected)
+
+    def test_parse_target_group_kind_rejects_invalid_value(self) -> None:
+        """Verify target group kind parsing rejects unknown names."""
+        with self.assertRaisesRegex(ValueError, "must be one of"):
+            _parse_target_group_kind("prefix")
+
+    def test_parse_target_group_kind_rejects_missing_or_any(self) -> None:
+        """Verify target group kind parsing requires an explicit concrete group."""
+        for raw in [None, "", "any", " Any "]:
+            with self.subTest(raw=raw):
+                with self.assertRaisesRegex(
+                    ValueError, "SGLANG_KV_CANARY_PERTURB_TARGET_GROUP"
+                ):
+                    _parse_target_group_kind(raw)
+
+    def test_from_env_allows_missing_target(
+        self,
+    ) -> None:
+        """Verify normal canary startup does not require a perturb target group."""
+        with patch.dict(os.environ, {}, clear=False):
+            os.environ.pop("SGLANG_KV_CANARY_PERTURB_TARGET_GROUP", None)
+            config = PerturbConfig.from_env()
+
+        self.assertIsNone(config.target_group_kind)
+
+
+if __name__ == "__main__":
+    unittest.main()