integration tests: Warn if test run changes network state

Ideally, the tests clean up after themselves. Try to catch differences
by comparing the host state from before and after the test run and warn
if there are differences.

Signed-off-by: Till Maas <opensource@till.name>

tests/integration/conftest.py

@@ -19,9 +19,12 @@
 
 import logging
 import subprocess
+import warnings
 
 import pytest
 
+import libnmstate
+
 from .testlib import ifacelib
 
 
@@ -39,7 +42,7 @@ def logging_setup():
 
 
 @pytest.fixture(scope='session', autouse=True)
-def ethx_init():
+def ethx_init(diff_initial_state):
     """ Remove any existing definitions on the ethX interfaces. """
     ifacelib.ifaces_init('eth1', 'eth2')
 
@@ -60,6 +63,23 @@ port0_up = eth1_up
 port1_up = eth2_up
 
 
+@pytest.fixture(scope='session', autouse=True)
+def diff_initial_state():
+    old_state = libnmstate.show()
+    yield
+    new_state = libnmstate.show()
+
+    if old_state != new_state:
+        warnings.warn(
+            'Network state after test run does not match network state '
+            'before test run:\n {}\n'.format(
+                libnmstate.prettystate.format_desired_current_state_diff(
+                    old_state, new_state
+                ),
+            )
+        )
+
+
 def pytest_report_header(config):
     return REPORT_HEADER.format(
         rpms=_get_package_nvr('NetworkManager'), osname=_get_osname()