network_test: Do not modify environment for other tests

Also do not skip the test since there will always be an interface (previously
set globally and now prepared in setUp function.

Author: nertpinx

test/network_test.py

@@ -14,10 +14,8 @@
 import can
 
 channel = "vcan0"
-can.rc["interface"] = "virtual"
 
 
-@unittest.skipIf("interface" not in can.rc, "Need a CAN interface")
 class ControllerAreaNetworkTestCase(unittest.TestCase):
     """
     This test ensures that what messages go in to the bus is what comes out.
@@ -42,6 +40,15 @@ class ControllerAreaNetworkTestCase(unittest.TestCase):
         for b in range(num_messages)
     )
 
+    def setUp(self):
+        # Save all can.rc defaults
+        self._can_rc = can.rc
+        can.rc = {"interface": "virtual"}
+
+    def tearDown(self):
+        # Restore the defaults
+        can.rc = self._can_rc
+
     def producer(self, ready_event, msg_read):
         self.client_bus = can.interface.Bus(channel=channel)
         ready_event.wait()