refactor: the CARP state table lives with the driver that speaks CARP

carp_virtual_ip() and its state table moved here from napalm-device-types
(4.10.1, NAPALM/napalm-device-types#39): under the agreed structure the base
package carries only the shape of the reading, and what a CARP state means is
protocol knowledge. Tests moved along (test_carp_states.py).

tests/unit/test_carp_states.py

@@ -0,0 +1,111 @@
+"""carp_virtual_ip: one CARP address as a virtual IP, with its holder in the reading.
+
+CARP differs from vip-manager and keepalived in what the caller can see. The
+address is configured on every member, and the interface list of a firewall need
+not show it at all -- so the interfaces cannot say who holds it. CARP's own state
+can: the member in MASTER holds it, a BACKUP stands by. That is CARP protocol
+knowledge, so it lives with the driver that speaks CARP (netOrk #1121), not in
+napalm-device-types.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from napalm_opnsense.virtual_ips import carp_virtual_ip
+
+
+def _entry(**overrides):
+    fields = {
+        "address": "172.22.8.1",
+        "prefix_length": 24,
+        "vhid": "108",
+        "state": "MASTER",
+        "instance": "MGMT",
+        "interface": "vtnet0",
+    }
+    fields.update(overrides)
+    return carp_virtual_ip(**fields)
+
+
+def test_a_master_holds_the_address():
+    assert _entry() == {
+        "mechanism": "carp",
+        "instance": "MGMT",
+        "address": "172.22.8.1",
+        "prefix_length": 24,
+        "interface": "vtnet0",
+        "group_key": "vhid:108",
+        "running": True,
+        "holds": True,
+    }
+
+
+def test_a_backup_stands_by():
+    entry = _entry(state="BACKUP")
+    assert entry is not None
+    assert (entry["running"], entry["holds"]) == (True, False)
+
+
+@pytest.mark.parametrize("state", ["INIT", "DISABLED"])
+def test_a_member_whose_carp_is_not_up_neither_runs_nor_holds(state):
+    entry = _entry(state=state)
+    assert entry is not None
+    assert (entry["running"], entry["holds"]) == (False, False)
+
+
+@pytest.mark.parametrize("state", [None, "", "SOMETHING-NEW"])
+def test_an_unknown_state_says_nothing_about_the_holder(state):
+    """None leaves the holder to the interfaces, as for the other mechanisms."""
+    entry = _entry(state=state)
+    assert entry is not None
+    assert (entry["running"], entry["holds"]) == (None, None)
+
+
+def test_the_state_is_read_case_blind():
+    entry = _entry(state=" master ")
+    assert entry is not None
+    assert entry["holds"] is True
+
+
+def test_the_address_is_normalised():
+    entry = _entry(address="FD00::0001", prefix_length=64)
+    assert entry is not None
+    assert entry["address"] == "fd00::1"
+
+
+def test_an_address_written_with_its_prefix_takes_that_prefix():
+    entry = _entry(address="10.42.100.1/24", prefix_length=None)
+    assert entry is not None
+    assert (entry["address"], entry["prefix_length"]) == ("10.42.100.1", 24)
+
+
+@pytest.mark.parametrize("address", ["", "not-an-address", "10.0.0.300"])
+def test_what_is_no_address_is_no_virtual_ip(address):
+    assert _entry(address=address) is None
+
+
+@pytest.mark.parametrize("prefix", [33, -1])
+def test_an_impossible_prefix_is_dropped(prefix):
+    entry = _entry(prefix_length=prefix)
+    assert entry is not None
+    assert entry["prefix_length"] is None
+
+
+@pytest.mark.parametrize("vhid", [None, "", "abc"])
+def test_without_a_numeric_vhid_there_is_no_group(vhid):
+    entry = _entry(vhid=vhid)
+    assert entry is not None
+    assert entry["group_key"] is None
+
+
+def test_a_vhid_given_as_a_number_groups_the_same_way():
+    entry = _entry(vhid=108)
+    assert entry is not None
+    assert entry["group_key"] == "vhid:108"
+
+
+def test_an_empty_instance_falls_back_to_the_vhid():
+    entry = _entry(instance="")
+    assert entry is not None
+    assert entry["instance"] == "vhid 108"