refactor(tests): centralize fake endpoint resolver cleanup

Test-only refactor continuing #2523. Centralizes the final repeated fake src.endpoint_resolver cleanup pattern into a focused import-state helper.

tests/test_helpers_import_state.py

@@ -6,6 +6,7 @@ import pytest
 
 from tests.helpers.import_state import (
     clear_fake_database_modules,
+    clear_fake_endpoint_resolver_modules,
     clear_module,
     preserve_import_state,
 )
@@ -16,6 +17,16 @@ _SENTINEL = "tests._import_state_test_sentinel"
 # tests never leak into the real core/src packages.
 _DB_NAMES = ("core", "core.database", "src", "src.database")
 
+# Names touched by clear_fake_endpoint_resolver_modules — snapshot/restore these
+# so the tests never leak into the real src/routes packages.
+_RESOLVER_NAMES = (
+    "src",
+    "src.endpoint_resolver",
+    "routes",
+    "routes.model_routes",
+    "routes.chat_routes",
+)
+
 
 def test_absent_module_is_removed_after_block():
     assert _SENTINEL not in sys.modules
@@ -250,3 +261,166 @@ def test_clear_fake_database_noop_when_nothing_cached():
         clear_fake_database_modules()  # must not raise
 
         assert "core.database" not in sys.modules
+
+
+def test_clear_fake_resolver_removes_stub_endpoint_resolver():
+    with preserve_import_state(*_RESOLVER_NAMES):
+        fake_src = types.ModuleType("src")
+        fake_resolver = types.ModuleType("src.endpoint_resolver")  # no __file__ => stub
+        fake_src.endpoint_resolver = fake_resolver
+        sys.modules["src"] = fake_src
+        sys.modules["src.endpoint_resolver"] = fake_resolver
+
+        clear_fake_endpoint_resolver_modules()
+
+        assert "src.endpoint_resolver" not in sys.modules
+        assert not hasattr(fake_src, "endpoint_resolver")
+
+
+def test_clear_fake_resolver_preserves_real_endpoint_resolver():
+    with preserve_import_state(*_RESOLVER_NAMES):
+        fake_src = types.ModuleType("src")
+        real_resolver = types.ModuleType("src.endpoint_resolver")
+        real_resolver.__file__ = "/somewhere/src/endpoint_resolver.py"  # looks on-disk
+        fake_src.endpoint_resolver = real_resolver
+        sys.modules["src"] = fake_src
+        sys.modules["src.endpoint_resolver"] = real_resolver
+
+        clear_fake_endpoint_resolver_modules()
+
+        assert sys.modules["src.endpoint_resolver"] is real_resolver
+        assert fake_src.endpoint_resolver is real_resolver
+
+
+def test_clear_fake_resolver_evicts_empty_file_resolver():
+    """A resolver with __file__ = "" is a stub under the old truthiness guard, so
+    it (and its dependents) must be evicted, not preserved."""
+    with preserve_import_state(*_RESOLVER_NAMES):
+        fake_src = types.ModuleType("src")
+        empty_resolver = types.ModuleType("src.endpoint_resolver")
+        empty_resolver.__file__ = ""  # falsy => stub
+        fake_src.endpoint_resolver = empty_resolver
+        sys.modules["src"] = fake_src
+        sys.modules["src.endpoint_resolver"] = empty_resolver
+        model_routes = types.ModuleType("routes.model_routes")
+        sys.modules["routes.model_routes"] = model_routes
+
+        clear_fake_endpoint_resolver_modules()
+
+        assert "src.endpoint_resolver" not in sys.modules
+        assert not hasattr(fake_src, "endpoint_resolver")
+        assert "routes.model_routes" not in sys.modules
+
+
+def test_clear_fake_resolver_removes_model_routes_when_resolver_fake():
+    """model_routes is dropped, and its parent `routes` attr is cleared too —
+    the behavior delta over the old bare sys.modules.pop() guards."""
+    with preserve_import_state(*_RESOLVER_NAMES):
+        fake_src = types.ModuleType("src")
+        fake_resolver = types.ModuleType("src.endpoint_resolver")
+        fake_src.endpoint_resolver = fake_resolver
+        sys.modules["src"] = fake_src
+        sys.modules["src.endpoint_resolver"] = fake_resolver
+
+        fake_routes = types.ModuleType("routes")
+        model_routes = types.ModuleType("routes.model_routes")
+        fake_routes.model_routes = model_routes
+        sys.modules["routes"] = fake_routes
+        sys.modules["routes.model_routes"] = model_routes
+
+        clear_fake_endpoint_resolver_modules()
+
+        assert "routes.model_routes" not in sys.modules
+        assert not hasattr(fake_routes, "model_routes")
+
+
+def test_clear_fake_resolver_removes_extra_modules_when_resolver_fake():
+    with preserve_import_state(*_RESOLVER_NAMES):
+        fake_src = types.ModuleType("src")
+        fake_resolver = types.ModuleType("src.endpoint_resolver")
+        fake_src.endpoint_resolver = fake_resolver
+        sys.modules["src"] = fake_src
+        sys.modules["src.endpoint_resolver"] = fake_resolver
+
+        fake_routes = types.ModuleType("routes")
+        chat_routes = types.ModuleType("routes.chat_routes")
+        fake_routes.chat_routes = chat_routes
+        sys.modules["routes"] = fake_routes
+        sys.modules["routes.chat_routes"] = chat_routes
+
+        clear_fake_endpoint_resolver_modules("routes.chat_routes")
+
+        assert "routes.chat_routes" not in sys.modules
+        assert not hasattr(fake_routes, "chat_routes")
+
+
+def test_clear_fake_resolver_keeps_dependents_when_resolver_real():
+    with preserve_import_state(*_RESOLVER_NAMES):
+        fake_src = types.ModuleType("src")
+        real_resolver = types.ModuleType("src.endpoint_resolver")
+        real_resolver.__file__ = "/somewhere/src/endpoint_resolver.py"
+        fake_src.endpoint_resolver = real_resolver
+        sys.modules["src"] = fake_src
+        sys.modules["src.endpoint_resolver"] = real_resolver
+
+        model_routes = types.ModuleType("routes.model_routes")
+        chat_routes = types.ModuleType("routes.chat_routes")
+        sys.modules["routes.model_routes"] = model_routes
+        sys.modules["routes.chat_routes"] = chat_routes
+
+        clear_fake_endpoint_resolver_modules("routes.chat_routes")
+
+        assert sys.modules["routes.model_routes"] is model_routes
+        assert sys.modules["routes.chat_routes"] is chat_routes
+
+
+def test_clear_fake_resolver_noop_when_nothing_cached():
+    with preserve_import_state(*_RESOLVER_NAMES):
+        sys.modules.pop("src.endpoint_resolver", None)
+        fake_src = types.ModuleType("src")  # no endpoint_resolver attr
+        sys.modules["src"] = fake_src
+        model_routes = types.ModuleType("routes.model_routes")
+        sys.modules["routes.model_routes"] = model_routes
+
+        clear_fake_endpoint_resolver_modules()  # must not raise
+
+        assert "src.endpoint_resolver" not in sys.modules
+        # dependents are left alone when the resolver was never cached
+        assert sys.modules["routes.model_routes"] is model_routes
+
+
+def test_clear_fake_resolver_keeps_parent_attr_pointing_elsewhere():
+    """When the cached src.endpoint_resolver is a stub but the `endpoint_resolver`
+    attr on the src package points at a *different* object, the attr is left
+    intact — only the same fake object is unlinked."""
+    with preserve_import_state(*_RESOLVER_NAMES):
+        fake_src = types.ModuleType("src")
+        cached_fake = types.ModuleType("src.endpoint_resolver")  # the stub in sys.modules
+        other = types.ModuleType("src.endpoint_resolver")  # parent attr points here
+        fake_src.endpoint_resolver = other
+        sys.modules["src"] = fake_src
+        sys.modules["src.endpoint_resolver"] = cached_fake
+
+        clear_fake_endpoint_resolver_modules()
+
+        assert "src.endpoint_resolver" not in sys.modules
+        assert fake_src.endpoint_resolver is other
+
+
+def test_clear_fake_resolver_uses_parent_attr_when_not_in_sys_modules():
+    """A stub reachable only via the src package's `endpoint_resolver` attribute
+    (not in sys.modules) is still detected, unlinked, and triggers dependent
+    eviction."""
+    with preserve_import_state(*_RESOLVER_NAMES):
+        sys.modules.pop("src.endpoint_resolver", None)
+        fake_src = types.ModuleType("src")
+        fake_resolver = types.ModuleType("src.endpoint_resolver")
+        fake_src.endpoint_resolver = fake_resolver
+        sys.modules["src"] = fake_src
+        model_routes = types.ModuleType("routes.model_routes")
+        sys.modules["routes.model_routes"] = model_routes
+
+        clear_fake_endpoint_resolver_modules()
+
+        assert not hasattr(fake_src, "endpoint_resolver")
+        assert "routes.model_routes" not in sys.modules