test_bootup: check not only for config for disabled network on boot

This adds additional test that tries if router really does not try to
receive address from DHCP even if not configured. This is even more
powerful test but thanks to need to blindly wait it can take some
considerable amount of time and thus does not replace test_no_wan but
complements it.

tests/test_bootup.py

 """These are test that check that everything we need is running after boot. This does simple and quick tests to catch
 general errors such as disabled core services.
 """
+import time
 import pytest
-from nsfarm.toolbox import service_is_running
+from nsfarm.lxd import Container
 from nsfarm.cli import Shell
+from nsfarm.toolbox import service_is_running
 
 
 def test_syslog_ng(client_board):
@@ -96,8 +98,34 @@ def test_lighttpd(lan1_client):
 
 
 def test_no_wan(client_board):
-    """The router should not have WAN interface configured to any valid setting as we want to force users to first go
-    trough first setup guide and set password there.
+    """Wan interface should be in default configured to none and thus disabled.
     """
     client_board.run("uci get network.wan.proto")
     assert client_board.output == "none"
+
+
+class TestNoInternetAccess:
+    """The router should not have WAN interface configured to any valid setting as we want to force users to first go
+    through first setup guide and set password there.
+    """
+
+    @pytest.fixture(scope="class", autouse=True)
+    def fixture_dhcp_isp(self, lxd, wan, client_board):
+        """This provides DHCP server on WAN interface the router could use to autoconfigure WAN if it would want to.
+        """
+        with Container(lxd, "isp-dhcp", devices=[wan, ]) as container:
+            Shell(container.pexpect()).run("wait4network")
+            client_board.run("/etc/init.d/network restart")  # Trigger network restart to force potential renew now
+            # Unfortunatelly we can't wait for router to pickup address as technically it should not. Instead we wait
+            # some amount of time we can expect it would picked up address from DHCP.
+            time.sleep(10)
+            yield container
+
+    @pytest.mark.parametrize("ipv", ["4", "6"])
+    def test_no_internet_access(self, client_board, ipv):
+        """Although test_no_wan checks if wan is not configured it does not mean that some automatic function might not
+        configure WAN. This checks that we really do not have the Internet access.
+        It is reasonable assumption that without default route there is no Internet access so it should be enough to
+        check if there is no default route.
+        """
+        assert client_board.run(f"ip -{ipv} route | grep -F 'default via'", None) == 1