diff --git a/src/yggdrasil/core_test.go b/src/yggdrasil/core_test.go
new file mode 100644
index 00000000..364ed0b0
--- /dev/null
+++ b/src/yggdrasil/core_test.go
@@ -0,0 +1,204 @@
+package yggdrasil
+
+import (
+	"bytes"
+	"math/rand"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/gologme/log"
+
+	"github.com/yggdrasil-network/yggdrasil-go/src/config"
+)
+
+// GenerateConfig produces default configuration with suitable modifications for tests.
+func GenerateConfig() *config.NodeConfig {
+	cfg := config.GenerateConfig()
+	cfg.AdminListen = "none"
+	cfg.Listen = []string{"tcp://127.0.0.1:0"}
+	cfg.IfName = "none"
+
+	return cfg
+}
+
+// GetLoggerWithPrefix creates a new logger instance wih prefix.
+// If verbose is set to true, three log levels are enabled: "info", "warn", "error".
+func GetLoggerWithPrefix(prefix string, verbose bool) *log.Logger {
+	l := log.New(os.Stderr, prefix, log.Flags())
+	if !verbose {
+		return l
+	}
+	l.EnableLevel("info")
+	l.EnableLevel("warn")
+	l.EnableLevel("error")
+	return l
+}
+
+// CreateAndConnectTwo creates two nodes. nodeB connects to nodeA.
+// Verbosity flag is passed to logger.
+func CreateAndConnectTwo(t testing.TB, verbose bool) (nodeA *Core, nodeB *Core) {
+	nodeA = new(Core)
+	_, err := nodeA.Start(GenerateConfig(), GetLoggerWithPrefix("A: ", verbose))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	nodeB = new(Core)
+	_, err = nodeB.Start(GenerateConfig(), GetLoggerWithPrefix("B: ", verbose))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = nodeB.AddPeer("tcp://"+nodeA.link.tcp.getAddr().String(), "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if l := len(nodeA.GetPeers()); l != 1 {
+		t.Fatal("unexpected number of peers", l)
+	}
+	if l := len(nodeB.GetPeers()); l != 1 {
+		t.Fatal("unexpected number of peers", l)
+	}
+
+	return nodeA, nodeB
+}
+
+// WaitConnected blocks until either nodes negotiated DHT or 5 seconds passed.
+func WaitConnected(nodeA, nodeB *Core) bool {
+	// It may take up to 3 seconds, but let's wait 5.
+	for i := 0; i < 50; i++ {
+		time.Sleep(100 * time.Millisecond)
+		if len(nodeA.GetSwitchPeers()) > 0 && len(nodeB.GetSwitchPeers()) > 0 {
+			return true
+		}
+	}
+	return false
+}
+
+// CreateEchoListener creates a routine listening on nodeA. It expects repeats messages of length bufLen.
+// It returns a channel used to synchronize the routine with caller.
+func CreateEchoListener(t testing.TB, nodeA *Core, bufLen int, repeats int) chan struct{} {
+	// Listen. Doing it here guarantees that there will be something to try to connect when it returns.
+	listener, err := nodeA.ConnListen()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Start routine
+	done := make(chan struct{})
+	go func() {
+		defer listener.Close()
+		conn, err := listener.Accept()
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		defer conn.Close()
+		buf := make([]byte, bufLen)
+
+		for i := 0; i < repeats; i++ {
+			n, err := conn.Read(buf)
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			if n != bufLen {
+				t.Error("missing data")
+				return
+			}
+			_, err = conn.Write(buf)
+			if err != nil {
+				t.Error(err)
+			}
+		}
+		done <- struct{}{}
+	}()
+
+	return done
+}
+
+// TestCore_Start_Connect checks if two nodes can connect together.
+func TestCore_Start_Connect(t *testing.T) {
+	CreateAndConnectTwo(t, true)
+}
+
+// TestCore_Start_Transfer checks that messages can be passed between nodes (in both directions).
+func TestCore_Start_Transfer(t *testing.T) {
+	nodeA, nodeB := CreateAndConnectTwo(t, true)
+
+	msgLen := 1500
+	done := CreateEchoListener(t, nodeA, msgLen, 1)
+
+	if !WaitConnected(nodeA, nodeB) {
+		t.Fatal("nodes did not connect")
+	}
+
+	// Dial
+	dialer, err := nodeB.ConnDialer()
+	if err != nil {
+		t.Fatal(err)
+	}
+	conn, err := dialer.Dial("nodeid", nodeA.NodeID().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+	msg := make([]byte, msgLen)
+	rand.Read(msg)
+	conn.Write(msg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	buf := make([]byte, msgLen)
+	_, err = conn.Read(buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if bytes.Compare(msg, buf) != 0 {
+		t.Fatal("expected echo")
+	}
+	<-done
+}
+
+// BenchmarkCore_Start_Transfer estimates the possible transfer between nodes (in MB/s).
+func BenchmarkCore_Start_Transfer(b *testing.B) {
+	nodeA, nodeB := CreateAndConnectTwo(b, false)
+
+	msgLen := 1500 // typical MTU
+	done := CreateEchoListener(b, nodeA, msgLen, b.N)
+
+	if !WaitConnected(nodeA, nodeB) {
+		b.Fatal("nodes did not connect")
+	}
+
+	// Dial
+	dialer, err := nodeB.ConnDialer()
+	if err != nil {
+		b.Fatal(err)
+	}
+	conn, err := dialer.Dial("nodeid", nodeA.NodeID().String())
+	if err != nil {
+		b.Fatal(err)
+	}
+	defer conn.Close()
+	msg := make([]byte, msgLen)
+	rand.Read(msg)
+	buf := make([]byte, msgLen)
+
+	b.SetBytes(int64(b.N * msgLen))
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		conn.Write(msg)
+		if err != nil {
+			b.Fatal(err)
+		}
+		_, err = conn.Read(buf)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+	<-done
+}