Add coverage for the delayed signal handler

Signed-off-by: Bernát Gábor <bgabor8@bloomberg.net>

3 files changed, 45 insertions, 2 deletions

diff --git a/src/tox/util/signal.py b/src/tox/util/signal.py
index e0cd8523..6d413a3b 100644
--- a/src/tox/util/signal.py
+++ b/src/tox/util/signal.py
@@ -12,10 +12,11 @@ class DelayedSignal:
         self._frame: Optional[FrameType] = None
         self._old_handler: Union[Callable[[Signals, FrameType], None], int, Handlers, None] = None
 
-    def __enter__(self) -> None:
+    def __enter__(self) -> "DelayedSignal":
         self._signal, self._frame = None, None
         if threading.current_thread() == threading.main_thread():  # signals are always handled on the main thread only
             self._old_handler = signal(self._of, self._handler)
+        return self
 
     def __exit__(
         self, exc_type: Optional[Type[BaseException]], exc_val: Optional[BaseException], exc_tb: Optional[TracebackType]
diff --git a/tests/execute/local_subprocess/test_local_subprocess.py b/tests/execute/local_subprocess/test_local_subprocess.py
index f7bbde03..b3864a25 100644
--- a/tests/execute/local_subprocess/test_local_subprocess.py
+++ b/tests/execute/local_subprocess/test_local_subprocess.py
@@ -205,7 +205,6 @@ def test_command_does_not_exist(capsys: CaptureFixture, caplog: LogCaptureFixtur
 
 
 @pytest.mark.skipif(sys.platform == "win32", reason="You need a conhost shell for keyboard interrupt")
-# @pytest.mark.timeout(10)
 def test_command_keyboard_interrupt(tmp_path: Path, monkeypatch: MonkeyPatch, capfd: CaptureFixture) -> None:
     monkeypatch.chdir(tmp_path)
     process_up_signal = tmp_path / "signal"
diff --git a/tests/util/test_signal.py b/tests/util/test_signal.py
new file mode 100644
index 00000000..6b2640fb
--- /dev/null
+++ b/tests/util/test_signal.py
@@ -0,0 +1,43 @@
+import logging
+import os
+import sys
+from threading import Thread
+from time import sleep
+
+import pytest
+
+from tox.execute.local_sub_process import SIG_INTERRUPT
+from tox.pytest import LogCaptureFixture
+from tox.util.signal import DelayedSignal
+
+
+@pytest.mark.skipif(sys.platform == "win32", reason="You need a conhost shell for keyboard interrupt")
+def test_signal_delayed(caplog: LogCaptureFixture) -> None:
+    caplog.set_level(level=logging.DEBUG)
+    with pytest.raises(KeyboardInterrupt):
+        with DelayedSignal() as handler:
+            try:
+                os.kill(os.getpid(), SIG_INTERRUPT)
+                while True:
+                    sleep(0.05)
+                    if handler._signal is not None:  # pragma: no branch
+                        break
+            except KeyboardInterrupt:  # pragma: no cover
+                assert False  # pragma: no cover
+    assert caplog.messages == [
+        "Received 2, delaying it",
+        "Handling delayed 2",
+    ]
+
+
+def test_signal_no_op_background(caplog: LogCaptureFixture) -> None:
+    caplog.set_level(level=logging.DEBUG)
+
+    def _run() -> None:
+        with DelayedSignal():
+            pass
+
+    thread = Thread(target=_run)
+    thread.start()
+    thread.join()
+    assert caplog.messages == []