Add a test for switch connection map handling

cmd/metal-api/internal/metal/switch.go

@@ -86,8 +86,8 @@ func (c ConnectionMap) ByNicName() (map[string]Connection, error) {
 	res := make(map[string]Connection)
 	for _, cons := range c {
 		for _, con := range cons {
-			if con2, has := res[con.Nic.Name]; has {
-				return nil, fmt.Errorf("connection map has duplicate connections for nic %s; con1: %v, con2: %v", con.Nic.Name, con, con2)
+			if _, has := res[con.Nic.Name]; has {
+				return nil, fmt.Errorf("switch port %s is connected to more than one machine", con.Nic.Name)
 			}
 			res[con.Nic.Name] = con
 		}

cmd/metal-api/internal/metal/switch_test.go

@@ -3,6 +3,8 @@ package metal
 import (
 	"reflect"
 	"testing"
+
+	"github.com/google/go-cmp/cmp"
 )
 
 var (
@@ -277,3 +279,73 @@ func TestSwitch_ConnectMachine2(t *testing.T) {
 		})
 	}
 }
+
+func TestConnectionMap_ByNicName(t *testing.T) {
+	tests := []struct {
+		name           string
+		c              ConnectionMap
+		want           map[string]Connection
+		wantErr        bool
+		wantErrmessage string
+	}{
+		{
+			name: "one machine connected to one switch",
+			c: ConnectionMap{
+				"m1": Connections{
+					Connection{MachineID: "m1", Nic: Nic{MacAddress: "11:11", Name: "swp1"}},
+				},
+			},
+			want: map[string]Connection{
+				"swp1": {MachineID: "m1", Nic: Nic{MacAddress: "11:11", Name: "swp1"}},
+			},
+			wantErr: false,
+		},
+		{
+			name: "two machines connected to one switch",
+			c: ConnectionMap{
+				"m1": Connections{
+					Connection{MachineID: "m1", Nic: Nic{MacAddress: "11:11", Name: "swp1"}},
+				},
+				"m2": Connections{
+					Connection{MachineID: "m2", Nic: Nic{MacAddress: "21:11", Name: "swp2"}},
+				},
+			},
+			want: map[string]Connection{
+				"swp1": {MachineID: "m1", Nic: Nic{MacAddress: "11:11", Name: "swp1"}},
+				"swp2": {MachineID: "m2", Nic: Nic{MacAddress: "21:11", Name: "swp2"}},
+			},
+			wantErr: false,
+		},
+		{
+			name: "two machines connected to one switch at the same port",
+			c: ConnectionMap{
+				"m1": Connections{
+					Connection{MachineID: "m1", Nic: Nic{MacAddress: "11:11", Name: "swp1"}},
+				},
+				"m2": Connections{
+					Connection{MachineID: "m2", Nic: Nic{MacAddress: "21:11", Name: "swp1"}},
+				},
+			},
+			want:           nil,
+			wantErr:        true,
+			wantErrmessage: "switch port swp1 is connected to more than one machine",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := tt.c.ByNicName()
+			if (err != nil) != tt.wantErr {
+				t.Errorf("ConnectionMap.ByNicName() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if tt.wantErr && tt.wantErrmessage != err.Error() {
+				t.Errorf("ConnectionMap.ByNicName() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+
+			if diff := cmp.Diff(tt.want, got); diff != "" {
+				t.Errorf("ConnectionMap.ByNicName() diff: %s", diff)
+			}
+		})
+	}
+}