tests: use mocks to allow calling virEventRegisterImpl many times

We currently have to run each of the test_aio.py test cases in a
separate process, because libvirt.virEventRegisterImpl can only be
called once per process. This leads to quite unpleasant console
output when running tests.

By introducing a mock for libvirt.virEventRegisterImpl we can
regain the ability to run everything in a single process. The only
caveat is that it relies on tests to fully cleanup, but in practice
this is ok for our current tests.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

2 files changed, 101 insertions, 9 deletions

diff --git a/tests/eventmock.py b/tests/eventmock.py
new file mode 100644
index 0000000..7298086
--- /dev/null
+++ b/tests/eventmock.py
@@ -0,0 +1,82 @@
+
+import libvirt
+import libvirtmod
+
+_add_handle_impl = None
+_update_handle_impl = None
+_remove_handle_impl = None
+
+_add_timeout_impl = None
+_update_timeout_impl = None
+_remove_timeout_impl = None
+
+_registered = False
+
+def _add_handle(fd: int, event: int, cb: libvirt._EventCB, opaque: libvirt._T) -> int:
+    global _add_handle_impl
+    assert _add_handle_impl != None
+    return _add_handle_impl(fd, event, cb, opaque)
+
+def _update_handle(watch: int, event: int) -> None:
+    global _update_handle_impl
+    assert _update_handle_impl != None
+    _update_handle_impl(watch, event)
+
+def _remove_handle(watch: int) -> int:
+    global _remove_handle_impl
+    assert _remove_handle_impl != None
+    return _remove_handle_impl(watch)
+
+def _add_timeout(timeout: int, cb: libvirt._TimerCB, opaque: libvirt._T) -> int:
+    global _add_timeout_impl
+    assert _add_timeout_impl != None
+    return _add_timeout_impl(timeout, cb, opaque)
+
+def _update_timeout(timer: int, timeout: int) -> None:
+    global _update_timeout_impl
+    assert _update_timeout_impl != None
+    _update_timeout_impl(timer, timeout)
+
+def _remove_timeout(timer: int) -> int:
+    global _remove_timeout_impl
+    assert _remove_timeout_impl != None
+    return _remove_timeout_impl(timer)
+
+# libvirt.virEventRegisterImpl() is a one time call per process
+# This method is intended to be used with mock patching, so that
+# tests can get the appearance of being able to call
+# virEventRegisterImpl many times.
+#
+# Note, this relies on the tests closing all connection objects
+# and not leaving any handles/timers pending when they stop
+# running their event loop impl.
+
+def virEventRegisterImplMock(add_handle_impl,
+                             update_handle_impl,
+                             remove_handle_impl,
+                             add_timeout_impl,
+                             update_timeout_impl,
+                             remove_timeout_impl):
+    global _add_handle_impl
+    global _update_handle_impl
+    global _remove_handle_impl
+    global _add_timeout_impl
+    global _update_timeout_impl
+    global _remove_timeout_impl
+
+    _add_handle_impl = add_handle_impl
+    _update_handle_impl = update_handle_impl
+    _remove_handle_impl = remove_handle_impl
+    _add_timeout_impl = add_timeout_impl
+    _update_timeout_impl = update_timeout_impl
+    _remove_timeout_impl = remove_timeout_impl
+
+    global _registered
+    if not _registered:
+        libvirtmod.virEventRegisterImpl(_add_handle,
+                                        _update_handle,
+                                        _remove_timeout,
+                                        _add_timeout,
+                                        _update_timeout,
+                                        _remove_timeout)
+        _registered = True
diff --git a/tests/test_aio.py b/tests/test_aio.py
index fb8c6b6..c90934d 100644
--- a/tests/test_aio.py
+++ b/tests/test_aio.py
@@ -3,7 +3,9 @@ import libvirt
 import libvirtaio
 import sys
 import unittest
-import pytest
+from unittest import mock
+
+import eventmock
 
 
 class TestLibvirtAio(unittest.TestCase):
@@ -70,8 +72,9 @@ class TestLibvirtAio(unittest.TestCase):
             if domainStopped:
                 dom.create()
 
-    @pytest.mark.separate_process
-    def testEventsWithManualLoopSetup(self):
+    @mock.patch('libvirt.virEventRegisterImpl',
+                side_effect=eventmock.virEventRegisterImplMock)
+    def testEventsWithManualLoopSetup(self, mock_event_register):
         loop = asyncio.new_event_loop()
         asyncio.set_event_loop(loop)
 
@@ -79,15 +82,19 @@ class TestLibvirtAio(unittest.TestCase):
 
         loop.close()
         asyncio.set_event_loop(None)
+        mock_event_register.assert_called_once()
 
-    @pytest.mark.separate_process
+    @mock.patch('libvirt.virEventRegisterImpl',
+                side_effect=eventmock.virEventRegisterImplMock)
     @unittest.skipIf(sys.version_info < (3,7), "test requires Python 3.7+")
-    def testEventsWithAsyncioRun(self):
+    def testEventsWithAsyncioRun(self, mock_event_register):
         asyncio.run(self._run(register=True))
+        mock_event_register.assert_called_once()
 
-    @pytest.mark.separate_process
+    @mock.patch('libvirt.virEventRegisterImpl',
+                side_effect=eventmock.virEventRegisterImplMock)
     @unittest.skipIf(sys.version_info >= (3,10), "test not compatible with Python 3.10+")
-    def testEventsPreInit(self):
+    def testEventsPreInit(self, mock_event_register):
         # Initialize libvirt events before setting the event loop. This is not recommended.
         # But is supported in older version of Python for the sake of back-compat.
         loop = asyncio.new_event_loop()
@@ -98,9 +105,11 @@ class TestLibvirtAio(unittest.TestCase):
 
         loop.close()
         asyncio.set_event_loop(None)
+        mock_event_register.assert_called_once()
 
-    @pytest.mark.separate_process
-    def testEventsImplicitLoopInit(self):
+    @mock.patch('libvirt.virEventRegisterImpl',
+                side_effect=eventmock.virEventRegisterImplMock)
+    def testEventsImplicitLoopInit(self, mock_event_register):
         # Allow virEventRegisterAsyncIOImpl() to init the event loop by calling
         # asyncio.get_event_loop(). This is not recommended and probably only works by
         # accident. But is supported for now for the sake of back-compat. For Python
@@ -112,3 +121,4 @@ class TestLibvirtAio(unittest.TestCase):
 
         loop.close()
         asyncio.set_event_loop(None)
+        mock_event_register.assert_called_once()