diff --git a/config.go b/config.go
deleted file mode 100644
index c314e8e..0000000
--- a/config.go
+++ /dev/null
@@ -1,28 +0,0 @@
-package main
-
-type paneConfig struct {
-	Dir     string
-	Zoom    bool
-	Split   string
-	Scripts []string
-}
-
-type windowConfig struct {
-	Name        string
-	Dir         string
-	Layout      string
-	Sync        bool
-	Scripts     []string
-	Panes       []paneConfig
-	PaneScripts []string `toml:"pane-scripts"`
-}
-
-type sessionConfig struct {
-	Name          string
-	Dir           string
-	ClearPanes    bool `toml:"clear-panes"`
-	Windows       []windowConfig
-	SelectWindow  string   `toml:"select-window"`
-	SelectPane    int      `toml:"select-pane"`
-	WindowScripts []string `toml:"window-scripts"`
-}
diff --git a/config/config.go b/config/config.go
new file mode 100644
index 0000000..5d55e07
--- /dev/null
+++ b/config/config.go
@@ -0,0 +1,114 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"io"
+
+	"github.com/BurntSushi/toml"
+)
+
+// Pane contains a pane configuration
+type Pane struct {
+	Dir     string
+	Zoom    bool
+	Split   string
+	Scripts []string
+}
+
+// Window contains a window configuration
+type Window struct {
+	Name        string
+	Dir         string
+	Layout      string
+	Sync        bool
+	Scripts     []string
+	Panes       []Pane
+	PaneScripts []string `toml:"pane-scripts"`
+}
+
+// Session contains a tmux session configuration
+type Session struct {
+	Name          string
+	Dir           string
+	ClearPanes    bool `toml:"clear-panes"`
+	Windows       []Window
+	SelectWindow  string   `toml:"select-window"`
+	SelectPane    int      `toml:"select-pane"`
+	WindowScripts []string `toml:"window-scripts"`
+}
+
+var (
+	validLayouts = []string{
+		"even-horizontal",
+		"even-vertical",
+		"main-horizontal",
+		"main-vertical",
+		"tiled",
+	}
+)
+
+func checkValid(conf Session) error {
+	// check at least one window
+	if len(conf.Windows) == 0 {
+		return errors.New("you must declare at least on window (0 provided)")
+	}
+
+	// check select-window and select-pane exist
+	if conf.SelectWindow != "" {
+		var win Window
+		found := false
+		for _, w := range conf.Windows {
+			if w.Name == conf.SelectWindow {
+				win = w
+				found = true
+				break
+			}
+		}
+
+		if !found {
+			return fmt.Errorf("selected window %s doesn't exist", conf.SelectWindow)
+		}
+
+		if conf.SelectPane != 0 {
+			if len(win.Panes) < conf.SelectPane {
+				return fmt.Errorf("selected pane %d doesn't exist", conf.SelectPane)
+			}
+		}
+	}
+
+	for _, w := range conf.Windows {
+		if w.Layout != "" {
+			found := false
+			for _, l := range validLayouts {
+				if l == w.Layout {
+					found = true
+				}
+			}
+
+			if !found {
+				return fmt.Errorf("invalid layout '%s' in window '%s'", w.Layout, w.Name)
+			}
+		}
+	}
+
+	// check only on zoom in a window
+
+	return nil
+}
+
+// Parse return a sessionConfig from a io.Reader
+func Parse(reader io.ReadCloser) (Session, error) {
+	defer reader.Close()
+
+	var conf Session
+	if _, err := toml.DecodeReader(reader, &conf); err != nil {
+		return conf, fmt.Errorf("parsing configuration: %v", err)
+	}
+
+	if err := checkValid(conf); err != nil {
+		return conf, err
+	}
+
+	return conf, nil
+}
diff --git a/main.go b/main.go
index f504f22..0e47a9b 100644
--- a/main.go
+++ b/main.go
@@ -5,16 +5,16 @@ import (
 	"log"
 	"os"
 
-	"github.com/BurntSushi/toml"
 	"github.com/alecthomas/kingpin"
 	"github.com/alexandrebodin/go-findup"
+	"github.com/alexandrebodin/tmuxctl/config"
 	"github.com/alexandrebodin/tmuxctl/tmux"
 )
 
 var (
-	version = "development"
-	start   = kingpin.Command("start", "start a tmux instance").Default()
-	config  = start.Arg("config", "Tmux config file").Default(".tmuxctlrc").String()
+	version    = "development"
+	start      = kingpin.Command("start", "start a tmux instance").Default()
+	configPath = start.Arg("config", "Tmux config file").Default(".tmuxctlrc").String()
 )
 
 func main() {
@@ -23,16 +23,21 @@ func main() {
 	kingpin.CommandLine.VersionFlag.Short('v')
 	kingpin.Parse()
 
-	fmt.Printf("Start tmux with config file: %v\n", *config)
+	fmt.Printf("Start tmux with config file: %v\n", *configPath)
 
-	filePath, err := findup.Find(*config)
+	filePath, err := findup.Find(*configPath)
 	if err != nil {
 		log.Fatalf("Error locating config file %v\n", err)
 	}
 
-	var conf sessionConfig
-	if _, err := toml.DecodeFile(filePath, &conf); err != nil {
-		log.Fatalf("Error loading configuration %v\n", err)
+	file, err := os.Open(filePath)
+	if err != nil {
+		log.Fatalf("Error openning config file %v\n", err)
+	}
+
+	conf, err := config.Parse(file)
+	if err != nil {
+		log.Fatalf("Error parsing %s: %v\n", filePath, err)
 	}
 
 	runningSessions, err := tmux.ListSessions()
diff --git a/pane.go b/pane.go
index 27c6c5b..96812a1 100644
--- a/pane.go
+++ b/pane.go
@@ -3,6 +3,7 @@ package main
 import (
 	"strconv"
 
+	"github.com/alexandrebodin/tmuxctl/config"
 	"github.com/alexandrebodin/tmuxctl/tmux"
 )
 
@@ -15,7 +16,7 @@ type pane struct {
 	Target  string
 }
 
-func newPane(win *window, config paneConfig, index int) *pane {
+func newPane(win *window, config config.Pane, index int) *pane {
 	normalizedIndex := strconv.Itoa(index + win.Sess.TmuxOptions.PaneBaseIndex)
 	pane := &pane{
 		Window:  win,
diff --git a/session.go b/session.go
index 1b5dac2..d1a6ef0 100644
--- a/session.go
+++ b/session.go
@@ -7,6 +7,7 @@ import (
 	"os/exec"
 	"syscall"
 
+	"github.com/alexandrebodin/tmuxctl/config"
 	"github.com/alexandrebodin/tmuxctl/tmux"
 )
 
@@ -19,7 +20,7 @@ type session struct {
 	WindowScripts []string
 }
 
-func newSession(config sessionConfig, options *tmux.Options) *session {
+func newSession(config config.Session, options *tmux.Options) *session {
 	sess := &session{
 		Name:          config.Name,
 		Dir:           lookupDir(config.Dir),
diff --git a/tmux/commands.go b/tmux/commands.go
index 9eb4cc0..412dece 100644
--- a/tmux/commands.go
+++ b/tmux/commands.go
@@ -1,116 +1,31 @@
 package tmux
 
-import (
-	"bytes"
-	"fmt"
-	"os/exec"
-	"strconv"
-	"strings"
+var (
+	// DefaultRunner is the default tmux command runner
+	DefaultRunner = &Runner{}
 )
 
-// Result is a commadn result
-type Result struct {
-	Stdout string
-	Stderr string
-}
-
 // Exec runs a tmux command
 func Exec(args ...string) (Result, error) {
-	var stdin bytes.Buffer
-	var stderr bytes.Buffer
-	var stdout bytes.Buffer
-
-	cmd := exec.Command("tmux", args...)
-	cmd.Stdin = &stdin
-	cmd.Stdout = &stdout
-	cmd.Stderr = &stderr
-
-	err := cmd.Run()
-	if err != nil {
-		return Result{}, fmt.Errorf("Error running command \"tmux %v\", %s", args, stderr.String())
-	}
-
-	return Result{stdout.String(), stderr.String()}, nil
+	return DefaultRunner.Exec(args...)
 }
 
 // SendKeys sends keys to tmux (e.g to run a command)
 func SendKeys(target, keys string) error {
-	_, err := Exec("send-keys", "-R", "-t", target, keys, "C-m")
-	return err
+	return DefaultRunner.SendKeys(target, keys)
 }
 
 // SendRawKeys sends keys to tmux (e.g to run a command)
 func SendRawKeys(target, keys string) error {
-	_, err := Exec("send-keys", "-R", "-t", target, keys)
-	return err
+	return DefaultRunner.SendRawKeys(target, keys)
 }
 
-// SessionInfo infos about a running tmux session
-type SessionInfo struct{}
-
 // ListSessions returns the list of sessions currently running
 func ListSessions() (map[string]SessionInfo, error) {
-	sessionMap := make(map[string]SessionInfo)
-
-	res, err := Exec("ls")
-	if err != nil {
-		if strings.Contains(err.Error(), "no server running on") {
-			return sessionMap, nil
-		}
-		return sessionMap, fmt.Errorf("error listing sessions %v", err)
-	}
-
-	splits := strings.Split(res.Stdout, "\n")
-	for _, sess := range splits {
-		sessSplits := strings.Split(sess, ":")
-		if len(sessSplits) > 1 {
-			sessionMap[sessSplits[0]] = SessionInfo{}
-		}
-	}
-
-	return sessionMap, nil
-}
-
-// Options tmux options
-type Options struct {
-	BaseIndex     int
-	PaneBaseIndex int
+	return DefaultRunner.ListSessions()
 }
 
 // GetOptions get tmux options
 func GetOptions() (*Options, error) {
-	options := &Options{
-		BaseIndex:     0,
-		PaneBaseIndex: 0,
-	}
-
-	var stderr bytes.Buffer
-	var stdout bytes.Buffer
-	cmd := exec.Command("sh", "-c", "tmux start-server\\; show-options -g\\; show-window-options -g")
-	cmd.Stdout = &stdout
-
-	err := cmd.Run()
-	if err != nil {
-		return options, fmt.Errorf("Error getting tmux options %v, %s", err, stderr.String())
-	}
-
-	optionsString := strings.Split(stdout.String(), "\n")
-	for _, option := range optionsString {
-		optionSplits := strings.Split(option, " ")
-		if len(optionSplits) == 2 {
-			name := optionSplits[0]
-			if name == "base-index" {
-				if v, err := strconv.Atoi(optionSplits[1]); err == nil {
-					options.BaseIndex = v
-				}
-			} else if name == "pane-base-index" {
-				if v, err := strconv.Atoi(optionSplits[1]); err == nil {
-					options.PaneBaseIndex = v
-				}
-
-			}
-		}
-	}
-
-	return options, nil
+	return DefaultRunner.GetOptions()
 }
diff --git a/tmux/runner.go b/tmux/runner.go
new file mode 100644
index 0000000..0a38043
--- /dev/null
+++ b/tmux/runner.go
@@ -0,0 +1,119 @@
+package tmux
+
+import (
+	"bytes"
+	"fmt"
+	"os/exec"
+	"strconv"
+	"strings"
+)
+
+// Runner is the underlying struct to run tmux commands
+type Runner struct{}
+
+// Options tmux options
+type Options struct {
+	BaseIndex     int
+	PaneBaseIndex int
+}
+
+// Result is a commadn result
+type Result struct {
+	Stdout string
+	Stderr string
+}
+
+// Exec runs a command
+func (r *Runner) Exec(args ...string) (Result, error) {
+	var stdin bytes.Buffer
+	var stderr bytes.Buffer
+	var stdout bytes.Buffer
+
+	cmd := exec.Command("tmux", args...)
+	cmd.Stdin = &stdin
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	err := cmd.Run()
+	if err != nil {
+		return Result{}, fmt.Errorf("Error running command \"tmux %v\", %s", args, stderr.String())
+	}
+
+	return Result{stdout.String(), stderr.String()}, nil
+}
+
+// SendKeys sends keys to tmux (e.g to run a command)
+func (r *Runner) SendKeys(target, keys string) error {
+	_, err := r.Exec("send-keys", "-R", "-t", target, keys, "C-m")
+	return err
+}
+
+// SendRawKeys sends keys to tmux (e.g to run a command)
+func (r *Runner) SendRawKeys(target, keys string) error {
+	_, err := Exec("send-keys", "-R", "-t", target, keys)
+	return err
+}
+
+// SessionInfo infos about a running tmux session
+type SessionInfo struct{}
+
+// ListSessions returns the list of sessions currently running
+func (r *Runner) ListSessions() (map[string]SessionInfo, error) {
+	sessionMap := make(map[string]SessionInfo)
+
+	res, err := Exec("ls")
+	if err != nil {
+		if strings.Contains(err.Error(), "no server running on") {
+			return sessionMap, nil
+		}
+		return sessionMap, fmt.Errorf("error listing sessions %v", err)
+	}
+
+	splits := strings.Split(res.Stdout, "\n")
+	for _, sess := range splits {
+		sessSplits := strings.Split(sess, ":")
+		if len(sessSplits) > 1 {
+			sessionMap[sessSplits[0]] = SessionInfo{}
+		}
+	}
+
+	return sessionMap, nil
+}
+
+// GetOptions get tmux options
+func (r *Runner) GetOptions() (*Options, error) {
+	options := &Options{
+		BaseIndex:     0,
+		PaneBaseIndex: 0,
+	}
+
+	var stderr bytes.Buffer
+	var stdout bytes.Buffer
+	cmd := exec.Command("sh", "-c", "tmux start-server\\; show-options -g\\; show-window-options -g")
+	cmd.Stdout = &stdout
+
+	err := cmd.Run()
+	if err != nil {
+		return options, fmt.Errorf("Error getting tmux options %v, %s", err, stderr.String())
+	}
+
+	optionsString := strings.Split(stdout.String(), "\n")
+	for _, option := range optionsString {
+		optionSplits := strings.Split(option, " ")
+		if len(optionSplits) == 2 {
+			name := optionSplits[0]
+			if name == "base-index" {
+				if v, err := strconv.Atoi(optionSplits[1]); err == nil {
+					options.BaseIndex = v
+				}
+			} else if name == "pane-base-index" {
+				if v, err := strconv.Atoi(optionSplits[1]); err == nil {
+					options.PaneBaseIndex = v
+				}
+
+			}
+		}
+	}
+
+	return options, nil
+}
diff --git a/window.go b/window.go
index 3a799be..35f033d 100644
--- a/window.go
+++ b/window.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/alexandrebodin/tmuxctl/config"
 	"github.com/alexandrebodin/tmuxctl/tmux"
 )
 
@@ -19,7 +20,7 @@ type window struct {
 	Target      string
 }
 
-func newWindow(sess *session, config windowConfig) *window {
+func newWindow(sess *session, config config.Window) *window {
 	win := &window{
 		Sess:        sess,
 		Name:        config.Name,