test: Add unit tests for zone-redundant load balancers

Add comprehensive unit tests for zone-redundant load balancer functionality:

- Add test fixture (fakeInternalAPILBSpecWithZones) with zone configuration
- Add test case to verify zones are correctly set on frontend IP configs
- Validate that zones array contains all expected zone values (1, 2, 3)
- Ensure zones are properly converted to Azure SDK format

The tests verify that the service layer correctly translates the API spec
into Azure SDK structures with zones on frontend IP configurations.

Author: bryan-cox

azure/services/loadbalancers/loadbalancers_test.go

@@ -111,6 +111,30 @@ var (
 		APIServerPort: 6443,
 	}
 
+	fakeInternalAPILBSpecWithZones = LBSpec{
+		Name:                 "my-private-lb",
+		ResourceGroup:        "my-rg",
+		SubscriptionID:       "123",
+		ClusterName:          "my-cluster",
+		Location:             "my-location",
+		Role:                 infrav1.APIServerRole,
+		Type:                 infrav1.Internal,
+		SKU:                  infrav1.SKUStandard,
+		SubnetName:           "my-cp-subnet",
+		BackendPoolName:      "my-private-lb-backendPool",
+		IdleTimeoutInMinutes: ptr.To[int32](4),
+		AvailabilityZones:    []string{"1", "2", "3"},
+		FrontendIPConfigs: []infrav1.FrontendIP{
+			{
+				Name: "my-private-lb-frontEnd",
+				FrontendIPClass: infrav1.FrontendIPClass{
+					PrivateIPAddress: "10.0.0.10",
+				},
+			},
+		},
+		APIServerPort: 6443,
+	}
+
 	fakeNodeOutboundLBSpec = LBSpec{
 		Name:                 "my-cluster",
 		ResourceGroup:        "my-rg",

azure/services/loadbalancers/spec_test.go

@@ -178,6 +178,22 @@ func TestParameters(t *testing.T) {
 			},
 			expectedError: "",
 		},
+		{
+			name:     "internal load balancer with availability zones",
+			spec:     &fakeInternalAPILBSpecWithZones,
+			existing: nil,
+			expect: func(g *WithT, result interface{}) {
+				g.Expect(result).To(BeAssignableToTypeOf(armnetwork.LoadBalancer{}))
+				lb := result.(armnetwork.LoadBalancer)
+				// Verify zones are set on frontend IP configuration
+				g.Expect(lb.Properties.FrontendIPConfigurations).To(HaveLen(1))
+				g.Expect(lb.Properties.FrontendIPConfigurations[0].Zones).To(HaveLen(3))
+				g.Expect(*lb.Properties.FrontendIPConfigurations[0].Zones[0]).To(Equal("1"))
+				g.Expect(*lb.Properties.FrontendIPConfigurations[0].Zones[1]).To(Equal("2"))
+				g.Expect(*lb.Properties.FrontendIPConfigurations[0].Zones[2]).To(Equal("3"))
+			},
+			expectedError: "",
+		},
 	}
 	for _, tc := range testcases {
 		t.Run(tc.name, func(t *testing.T) {