Add port checking functionality and tests

pkg/connection/port_test.go

@@ -0,0 +1,65 @@
+package connection
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_portAvailable(t *testing.T) {
+	assert.Equal(t, true, portAvailable(8081))
+
+	serv, err := net.Listen("tcp", "127.0.0.1:8081")
+	if err != nil {
+		fmt.Println(os.Stderr, "Unable to start test tcp listener:", err)
+		t.Fail()
+		return
+	}
+	defer serv.Close()
+
+	go func() {
+		for {
+			conn, err := serv.Accept()
+			if err == nil {
+				conn.Close()
+			}
+		}
+	}()
+
+	assert.Equal(t, false, portAvailable(8081))
+	assert.Equal(t, true, portAvailable(8082))
+}
+
+func Test_getAvailablePort(t *testing.T) {
+	port, err := getAvailablePort(8081, 1)
+	assert.Equal(t, nil, err)
+	assert.Equal(t, 8081, port)
+
+	serv, err := net.Listen("tcp", "127.0.0.1:8081")
+	if err != nil {
+		fmt.Println(os.Stderr, "Unable to start test tcp listener:", err)
+		t.Fail()
+		return
+	}
+	defer serv.Close()
+
+	go func() {
+		for {
+			conn, err := serv.Accept()
+			if err == nil {
+				conn.Close()
+			}
+		}
+	}()
+
+	port, err = getAvailablePort(8081, 0)
+	assert.EqualError(t, err, "No available port")
+	assert.Equal(t, -1, port)
+
+	port, err = getAvailablePort(8081, 1)
+	assert.Equal(t, nil, err)
+	assert.Equal(t, 8082, port)
+}