Add comprehensive tests for Equipment context

Added 6 new tests to improve coverage:
- list_snmp_enabled_equipment/0 for SNMP-enabled equipment filtering
- update_snmp_poll_time/1 for updating polling timestamps
- create_event/1 for creating equipment events with proper schema
- list_equipment_events/2 for event retrieval and ordering
- list_equipment_events/2 with limit parameter

This improves Equipment coverage from 87.50% to higher.

test/towerops/equipment_test.exs

@@ -163,5 +163,133 @@ defmodule Towerops.EquipmentTest do
       # But checked_at should be updated
       assert DateTime.after?(updated.last_checked_at, first_checked_at)
     end
+
+    test "list_snmp_enabled_equipment/0 returns only equipment with SNMP enabled", %{site: site} do
+      {:ok, snmp_enabled} =
+        Equipment.create_equipment(%{
+          name: "SNMP Router",
+          ip_address: "192.168.1.1",
+          site_id: site.id,
+          snmp_enabled: true,
+          snmp_community: "public"
+        })
+
+      {:ok, _snmp_disabled} =
+        Equipment.create_equipment(%{
+          name: "Non-SNMP Router",
+          ip_address: "192.168.1.2",
+          site_id: site.id,
+          snmp_enabled: false
+        })
+
+      result = Equipment.list_snmp_enabled_equipment()
+      assert length(result) == 1
+      assert hd(result).id == snmp_enabled.id
+    end
+
+    test "update_snmp_poll_time/1 updates last_snmp_poll_at timestamp", %{site: site} do
+      {:ok, equipment} = Equipment.create_equipment(Map.put(@valid_attrs, :site_id, site.id))
+      assert equipment.last_snmp_poll_at == nil
+
+      assert {:ok, updated} = Equipment.update_snmp_poll_time(equipment)
+      assert updated.last_snmp_poll_at
+      assert DateTime.before?(updated.last_snmp_poll_at, DateTime.utc_now())
+    end
+  end
+
+  describe "events" do
+    import Towerops.AccountsFixtures
+
+    alias Towerops.Equipment.Event
+
+    setup do
+      user = user_fixture()
+      {:ok, organization} = Towerops.Organizations.create_organization(%{name: "Test Org"}, user.id)
+
+      {:ok, site} =
+        Towerops.Sites.create_site(%{
+          name: "Test Site",
+          organization_id: organization.id
+        })
+
+      {:ok, equipment} =
+        Equipment.create_equipment(%{
+          name: "Router 1",
+          ip_address: "192.168.1.1",
+          site_id: site.id
+        })
+
+      %{equipment: equipment}
+    end
+
+    test "create_event/1 creates an equipment event", %{equipment: equipment} do
+      attrs = %{
+        equipment_id: equipment.id,
+        event_type: "interface_up",
+        severity: "info",
+        message: "Interface came online",
+        metadata: %{"interface" => "eth0"},
+        occurred_at: DateTime.truncate(DateTime.utc_now(), :second)
+      }
+
+      assert {:ok, %Event{} = event} = Equipment.create_event(attrs)
+      assert event.equipment_id == equipment.id
+      assert event.event_type == "interface_up"
+      assert event.severity == "info"
+      assert event.message == "Interface came online"
+      assert event.metadata == %{"interface" => "eth0"}
+    end
+
+    test "create_event/1 with invalid data returns error changeset" do
+      assert {:error, %Ecto.Changeset{}} = Equipment.create_event(%{})
+    end
+
+    test "list_equipment_events/2 returns events for equipment ordered by most recent", %{
+      equipment: equipment
+    } do
+      now = DateTime.utc_now()
+
+      {:ok, event1} =
+        Equipment.create_event(%{
+          equipment_id: equipment.id,
+          event_type: "interface_up",
+          severity: "info",
+          message: "Interface came up",
+          occurred_at: DateTime.add(now, -3600, :second)
+        })
+
+      {:ok, event2} =
+        Equipment.create_event(%{
+          equipment_id: equipment.id,
+          event_type: "interface_down",
+          severity: "warning",
+          message: "Interface went down",
+          occurred_at: DateTime.add(now, -1800, :second)
+        })
+
+      events = Equipment.list_equipment_events(equipment.id)
+      assert length(events) == 2
+      # Should be ordered by most recent first
+      assert hd(events).id == event2.id
+      assert List.last(events).id == event1.id
+    end
+
+    test "list_equipment_events/2 limits results", %{equipment: equipment} do
+      now = DateTime.utc_now()
+
+      # Create 10 events
+      for i <- 1..10 do
+        Equipment.create_event(%{
+          equipment_id: equipment.id,
+          event_type: "interface_down",
+          severity: "warning",
+          message: "Interface down event #{i}",
+          occurred_at: DateTime.add(now, -i * 60, :second)
+        })
+      end
+
+      events = Equipment.list_equipment_events(equipment.id, 5)
+      assert length(events) == 5
+    end
   end
 end