test(mutation): mutate rate_limiter.py live via a duckdb-free fixtureless test

pyproject.toml

@@ -206,14 +206,15 @@ asyncio_mode = "auto"
 # security-critical surfaces). It is a superset of what the CI gate actually
 # mutates: scripts/mutation_report.py drives the gate from its own
 # MODULE_TARGETS, which now mutates sdk/agentflow/retry.py,
-# src/serving/semantic_layer/sql_guard.py AND src/serving/masking.py live. The
-# serving modules are mutated as a top-level `serving` package against duckdb-free
-# narrow tests: mutmut's trampoline rejects a module name starting with `src.`,
-# which (not duckdb) was the real blocker. The remaining serving modules below
-# stay declared-only for now -- their unit tests pull the duckdb-backed query
-# engine, so mutating them in isolation needs a duckdb-free test per module (the
-# pattern sql_guard and masking now use); the blocker is the test import chain,
-# not the module. See scripts/mutation_report.py.
+# src/serving/semantic_layer/sql_guard.py, src/serving/masking.py AND
+# src/serving/api/rate_limiter.py live. The serving modules are mutated as a
+# top-level `serving` package against duckdb-free narrow tests: mutmut's
+# trampoline rejects a module name starting with `src.`, which (not duckdb) was
+# the real blocker. The remaining serving modules below stay declared-only for
+# now -- their unit tests pull the duckdb-backed query engine, so mutating them
+# in isolation needs a duckdb-free test per module (the pattern sql_guard,
+# masking and rate_limiter now use); the blocker is the test import chain, not
+# the module. See scripts/mutation_report.py.
 paths_to_mutate = [
     "src/serving/api/auth/manager.py",
     "src/serving/api/auth/key_rotation.py",

scripts/mutation_report.py

@@ -29,13 +29,17 @@ class ModuleTarget:
 # that, not duckdb, was the real blocker for the serving modules. The fix is to
 # (a) copy the module so it imports as a top-level package and (b) pair it with a
 # NARROW test that does not pull the duckdb-backed engine import chain. So
-# retry.py mutates as agentflow.retry (from sdk/agentflow), and sql_guard and
-# masking mutate as serving.* (from src/serving) against duckdb-free tests. Each
-# duckdb-free test also avoids fixtures and calls the module's methods directly:
-# under mutate_only_covered_lines a fixture-built object left every method line
-# uncovered, so only __init__ got mutated. The remaining serving modules whose
-# tests still need the duckdb engine (the query/auth surfaces) stay declared-only
-# in the [tool.mutmut] policy until they get duckdb-free unit tests of their own.
+# retry.py mutates as agentflow.retry (from sdk/agentflow), and sql_guard,
+# masking and rate_limiter mutate as serving.* (from src/serving) against
+# duckdb-free tests. Each duckdb-free test also avoids fixtures and calls the
+# module's methods directly: under mutate_only_covered_lines a fixture-built
+# object left every method line uncovered, so only __init__ got mutated.
+# rate_limiter additionally imports `from src.constants import ...`; its test
+# registers a tiny src.constants stub before importing the module, because the
+# serving workspace copies src/serving -> top-level `serving` without `src`. The
+# remaining serving modules whose tests still need the duckdb engine (the
+# query/auth surfaces) stay declared-only in the [tool.mutmut] policy until they
+# get duckdb-free unit tests of their own.
 MODULE_TARGETS = {
     Path("agentflow/retry.py"): ModuleTarget(
         threshold=0.75,
@@ -49,6 +53,10 @@ class ModuleTarget:
         threshold=0.90,
         tests=("tests/unit/test_masking_mutation.py",),
     ),
+    Path("serving/api/rate_limiter.py"): ModuleTarget(
+        threshold=0.90,
+        tests=("tests/unit/test_rate_limiter_mutation.py",),
+    ),
 }
 
 STATUS_BY_EXIT_CODE = {

tests/unit/test_mutmut_policy.py

@@ -18,11 +18,11 @@
 #     assembled here.
 # NOTE: these are the *declared* targets (intent). Actual mutation execution is
 # gated by scripts/mutation_report.py (MODULE_TARGETS), which now runs retry.py,
-# sql_guard.py AND masking.py live (the serving modules via duckdb-free narrow
-# tests, mutated as a top-level `serving` package so mutmut's trampoline accepts
-# them). The other serving modules below stay declared-only until they get
-# duckdb-free unit tests of their own. These assertions guard the declared
-# policy, not live coverage.
+# sql_guard.py, masking.py AND rate_limiter.py live (the serving modules via
+# duckdb-free narrow tests, mutated as a top-level `serving` package so mutmut's
+# trampoline accepts them). The other serving modules below stay declared-only
+# until they get duckdb-free unit tests of their own. These assertions guard the
+# declared policy, not live coverage.
 REQUIRED_MUTATION_TARGETS = {
     "src/serving/semantic_layer/sql_guard.py",
     "src/serving/api/auth/manager.py",