NAT node can use the VMware NAT

On Windows and Mac OS this allow the NAT node to use the
VMware nat (it's always vmnet8). On Linux we still use the
libvirt NAT

tests/compute/builtin/nodes/test_nat.py

@@ -17,14 +17,12 @@
 
 import uuid
 import pytest
-from unittest.mock import MagicMock
-from tests.utils import asyncio_patch
+from unittest.mock import MagicMock, patch
 
 from gns3server.compute.builtin.nodes.nat import Nat
-from gns3server.compute.vpcs import VPCS
 
 
-def test_json(on_gns3vm, project):
+def test_json_gns3vm(on_gns3vm, project):
     nat = Nat("nat1", str(uuid.uuid4()), project, MagicMock())
     assert nat.__json__() == {
         "name": "nat1",
@@ -40,3 +38,24 @@ def test_json(on_gns3vm, project):
             }
         ]
     }
+
+
+def test_json_darwin(darwin_platform, project):
+    with patch("gns3server.utils.interfaces.interfaces", return_value=[
+            {"name": "eth0", "special": False, "type": "ethernet"},
+            {"name": "vmnet8", "special": True, "type": "ethernet"}]):
+        nat = Nat("nat1", str(uuid.uuid4()), project, MagicMock())
+    assert nat.__json__() == {
+        "name": "nat1",
+        "node_id": nat.id,
+        "project_id": project.id,
+        "status": "started",
+        "ports_mapping": [
+            {
+                "interface": "vmnet8",
+                "name": "nat0",
+                "port_number": 0,
+                "type": "ethernet"
+            }
+        ]
+    }