More tests.

tests/test_utils_reactorless.py

@@ -0,0 +1,50 @@
+from __future__ import annotations
+
+import sys
+
+import pytest
+
+from scrapy.utils.reactorless import (
+    ReactorImportHook,
+    install_reactor_import_hook,
+    uninstall_reactor_import_hook,
+)
+
+
+class TestReactorImportHook:
+    def test_install_and_uninstall(self) -> None:
+        hook = install_reactor_import_hook()
+        try:
+            assert isinstance(hook, ReactorImportHook)
+            assert sys.meta_path[0] is hook
+        finally:
+            uninstall_reactor_import_hook(hook)
+        assert hook not in sys.meta_path
+
+    def test_uninstall_twice(self) -> None:
+        hook = install_reactor_import_hook()
+        uninstall_reactor_import_hook(hook)
+        uninstall_reactor_import_hook(hook)
+        assert hook not in sys.meta_path
+
+    def test_uninstall_not_installed(self) -> None:
+        uninstall_reactor_import_hook(ReactorImportHook())
+
+    def test_uninstall_only_removes_the_given_hook(self) -> None:
+        hook1 = install_reactor_import_hook()
+        hook2 = install_reactor_import_hook()
+        try:
+            uninstall_reactor_import_hook(hook1)
+            assert hook1 not in sys.meta_path
+            assert hook2 in sys.meta_path
+        finally:
+            uninstall_reactor_import_hook(hook1)
+            uninstall_reactor_import_hook(hook2)
+
+    def test_find_spec(self) -> None:
+        hook = ReactorImportHook()
+        with pytest.raises(
+            ImportError, match=r"Import of twisted\.internet\.reactor is forbidden"
+        ):
+            hook.find_spec("twisted.internet.reactor", None)
+        assert hook.find_spec("twisted.internet.defer", None) is None