More coverage improvements (#1035)

Author: blink1073

ipykernel/jsonutil.py

@@ -74,7 +74,7 @@ def encode_images(format_dict):
     return format_dict
 
 
-def json_clean(obj):
+def json_clean(obj):  # pragma: no cover
     """Deprecated, this is a no-op for jupyter-client>=7.
 
     Clean an object to ensure it's safe to encode in JSON.

ipykernel/tests/test_parentpoller.py

@@ -0,0 +1,39 @@
+import os
+import sys
+import warnings
+from unittest import mock
+
+import pytest
+
+from ipykernel.parentpoller import ParentPollerUnix, ParentPollerWindows
+
+
+@pytest.mark.skipif(os.name == "nt", reason="only works on posix")
+def test_parent_poller_unix():
+    poller = ParentPollerUnix()
+    with mock.patch("os.getppid", lambda: 1):
+
+        def exit_mock(*args):
+            sys.exit(1)
+
+        with mock.patch("os._exit", exit_mock), pytest.raises(SystemExit):
+            poller.run()
+
+    def mock_getppid():
+        raise ValueError("hi")
+
+    with mock.patch("os.getppid", mock_getppid), pytest.raises(ValueError):
+        poller.run()
+
+
+@pytest.mark.skipif(os.name != "nt", reason="only works on windows")
+def test_parent_poller_windows():
+    poller = ParentPollerWindows(interrupt_handle=1)
+
+    def mock_wait(*args, **kwargs):
+        return -1
+
+    with mock.patch("ctypes.windll.kernel32.WaitForMultipleObjects", mock_wait):
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore")
+            poller.run()

pyproject.toml

@@ -157,7 +157,8 @@ omit = [
   "ipykernel/tests/*",
   "ipykernel/debugger.py",
   "ipykernel/eventloops.py",
-  "ipykernel/pickleutil.py"
+  "ipykernel/pickleutil.py",
+  "ipykernel/serialize.py"
 ]
 
 [tool.flake8]