[#10] dialer: Fix formatting

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

balancer.go

@@ -3,6 +3,7 @@ package multinet
 import (
 	"context"
 	"errors"
+	"fmt"
 	"net"
 	"sync/atomic"
 )
@@ -18,6 +19,8 @@ const (
 	BalancerTypeRoundRobin BalancerType = "roundrobin"
 )
 
+var errNoSuitableNodeFound = errors.New("no suitale node found")
+
 type balancer interface {
 	DialContext(ctx context.Context, s *Subnet, network, address string) (net.Conn, error)
 }
@@ -39,7 +42,7 @@ func (r *roundRobin) DialContext(ctx context.Context, s *Subnet, network, addres
 		dd.LocalAddr = ii.LocalAddr
 		return r.d.dialContext(&dd, ctx, network, address)
 	}
-	return nil, errors.New("(*roundRobin).DialContext: no suitale node found")
+	return nil, fmt.Errorf("(*roundRobin).DialContext: %w", errNoSuitableNodeFound)
 }
 
 type firstEnabled struct {
@@ -57,5 +60,5 @@ func (r *firstEnabled) DialContext(ctx context.Context, s *Subnet, network, addr
 		dd.LocalAddr = ii.LocalAddr
 		return r.d.dialContext(&dd, ctx, network, address)
 	}
-	return nil, errors.New("(*firstEnabled).DialContext: no suitale node found")
+	return nil, fmt.Errorf("(*firstEnabled).DialContext: %w", errNoSuitableNodeFound)
 }

dialer_test.go

@@ -0,0 +1,58 @@
+package multinet
+
+import (
+	"context"
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestInterfacesDown(t *testing.T) {
+	t.Run("noop balancer", func(t *testing.T) {
+		d, err := NewDialer(Config{
+			Subnets:         []string{"10.11.12.0/24"},
+			InterfaceSource: testDownInterfaces,
+		})
+		require.NoError(t, err)
+		conn, err := d.DialContext(context.Background(), "tcp", "10.11.12.254:8080")
+		require.ErrorIs(t, err, errNoSuitableNodeFound)
+		require.Nil(t, conn)
+	})
+	t.Run("round robin balancer", func(t *testing.T) {
+		d, err := NewDialer(Config{
+			Subnets:         []string{"10.11.12.0/24"},
+			InterfaceSource: testDownInterfaces,
+			Balancer:        BalancerTypeRoundRobin,
+		})
+		require.NoError(t, err)
+		conn, err := d.DialContext(context.Background(), "tcp", "10.11.12.254:8080")
+		require.ErrorIs(t, err, errNoSuitableNodeFound)
+		require.Nil(t, conn)
+	})
+}
+
+func testDownInterfaces() ([]Interface, error) {
+	return []Interface{
+		&testInterface{
+			name: "data1",
+			addrs: []net.Addr{
+				&testAddr{
+					network: "tcp",
+					str:     "10.11.12.101/24",
+				},
+			},
+			down: true,
+		},
+		&testInterface{
+			name: "data2",
+			addrs: []net.Addr{
+				&testAddr{
+					network: "tcp",
+					str:     "10.11.12.102/24",
+				},
+			},
+			down: true,
+		},
+	}, nil
+}