diff --git a/app.go b/app.go
index 61033ed5..4dc7d052 100644
--- a/app.go
+++ b/app.go
@@ -13,7 +13,6 @@ import (
 	"bufio"
 	"crypto/tls"
 	"fmt"
-	"log"
 	"net"
 	"net/http"
 	"net/http/httputil"
@@ -307,7 +306,7 @@ func (app *App) Use(args ...interface{}) *Route {
 		case Handler:
 			handlers = append(handlers, arg)
 		default:
-			log.Fatalf("Use: Invalid Handler %v", reflect.TypeOf(arg))
+			panic(fmt.Sprintf("use: invalid handler %v\n", reflect.TypeOf(arg)))
 		}
 	}
 	return app.register(methodUse, prefix, handlers...)
@@ -492,7 +491,7 @@ func (app *App) Listen(address interface{}, tlsconfig ...*tls.Config) error {
 	// Start prefork
 	if app.Settings.Prefork {
 		if app.Settings.Network == "tcp6" || isIPv6(addr) {
-			log.Fatal("prefork does not support tcp6 networking")
+			return fmt.Errorf("listen: tcp6 is not supported when prefork is enabled")
 		}
 		return app.prefork(addr, tlsconfig...)
 	}
diff --git a/app_test.go b/app_test.go
index c7580751..2d4dcfc2 100644
--- a/app_test.go
+++ b/app_test.go
@@ -225,6 +225,28 @@ func Test_App_Use_Params(t *testing.T) {
 	resp, err = app.Test(httptest.NewRequest("GET", "/foo", nil))
 	utils.AssertEqual(t, nil, err, "app.Test(req)")
 	utils.AssertEqual(t, 200, resp.StatusCode, "Status code")
+
+	defer func() {
+		if err := recover(); err != nil {
+			utils.AssertEqual(t, "use: invalid handler func()\n", fmt.Sprintf("%v", err))
+		}
+	}()
+
+	app.Use("/:param/*", func() {
+		// this should panic
+	})
+}
+
+func Test_App_Add_Method_Test(t *testing.T) {
+	app := New()
+	defer func() {
+		if err := recover(); err != nil {
+			utils.AssertEqual(t, "add: invalid http method JOHN\n", fmt.Sprintf("%v", err))
+		}
+	}()
+	app.Add("JOHN", "/doe", func(c *Ctx) {
+
+	})
 }
 
 func Test_App_Use_Params_Group(t *testing.T) {
@@ -659,9 +681,7 @@ func Test_App_Next_Method(t *testing.T) {
 
 // go test -run Test_App_Listen
 func Test_App_Listen(t *testing.T) {
-	app := New(&Settings{
-		DisableStartupMessage: true,
-	})
+	app := New()
 
 	utils.AssertEqual(t, false, app.Listen(1.23) == nil)
 
diff --git a/group.go b/group.go
index bd853731..ab9b78e3 100644
--- a/group.go
+++ b/group.go
@@ -5,7 +5,7 @@
 package fiber
 
 import (
-	"log"
+	"fmt"
 	"reflect"
 )
 
@@ -32,7 +32,7 @@ func (grp *Group) Use(args ...interface{}) *Route {
 		case Handler:
 			handlers = append(handlers, arg)
 		default:
-			log.Fatalf("Use: Invalid Handler %v", reflect.TypeOf(arg))
+			panic(fmt.Sprintf("use: invalid handler %v\n", reflect.TypeOf(arg)))
 		}
 	}
 	return grp.app.register(methodUse, getGroupPath(grp.prefix, path), handlers...)
diff --git a/prefork_test.go b/prefork_test.go
index 2e850dfa..a904482b 100644
--- a/prefork_test.go
+++ b/prefork_test.go
@@ -13,7 +13,6 @@ func Test_App_Prefork_Child_Process(t *testing.T) {
 	defer os.Setenv(envPreforkChildKey, "")
 
 	app := New()
-	app.Settings.DisableStartupMessage = true
 	app.init()
 
 	err := app.prefork("invalid")
@@ -31,7 +30,6 @@ func Test_App_Prefork_Main_Process(t *testing.T) {
 	testPreforkMaster = true
 
 	app := New()
-	app.Settings.DisableStartupMessage = true
 	app.init()
 
 	go func() {
@@ -46,3 +44,16 @@ func Test_App_Prefork_Main_Process(t *testing.T) {
 	err := app.prefork("127.0.0.1:")
 	utils.AssertEqual(t, false, err == nil)
 }
+
+func Test_App_Prefork_TCP6_Addr(t *testing.T) {
+	app := New()
+	app.Settings.Prefork = true
+	app.Settings.DisableStartupMessage = true
+
+	app.init()
+	utils.AssertEqual(t, "listen: tcp6 is not supported when prefork is enabled", app.Listen("[::1]:3000").Error())
+
+	app.Settings.Network = "tcp6"
+	app.init()
+	utils.AssertEqual(t, "listen: tcp6 is not supported when prefork is enabled", app.Listen(":3000").Error())
+}
diff --git a/router.go b/router.go
index 09aad11e..ba436c0f 100644
--- a/router.go
+++ b/router.go
@@ -5,7 +5,7 @@
 package fiber
 
 import (
-	"log"
+	"fmt"
 	"strings"
 	"time"
 
@@ -147,11 +147,11 @@ func (app *App) register(method, pathRaw string, handlers ...Handler) *Route {
 	method = utils.ToUpper(method)
 	// Check if the HTTP method is valid unless it's USE
 	if methodInt(method) == -1 {
-		log.Fatalf("Add: Invalid HTTP method %s", method)
+		panic(fmt.Sprintf("add: invalid http method %s\n", method))
 	}
 	// A route requires atleast one ctx handler
 	if len(handlers) == 0 {
-		log.Fatalf("Missing func(c *fiber.Ctx) handler in route: %s", pathRaw)
+		panic(fmt.Sprintf("missing handler in route: %s\n", pathRaw))
 	}
 	// Cannot have an empty path
 	if pathRaw == "" {
diff --git a/router_test.go b/router_test.go
index bb0289e0..71a2e33c 100644
--- a/router_test.go
+++ b/router_test.go
@@ -8,6 +8,7 @@ package fiber
 
 import (
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
 	"net/http/httptest"
 	"testing"
@@ -204,6 +205,16 @@ func Test_Route_Match_Middleware_Root(t *testing.T) {
 	utils.AssertEqual(t, "middleware", getString(body))
 }
 
+func Test_Router_Register_Missing_Handler(t *testing.T) {
+	app := New()
+	defer func() {
+		if err := recover(); err != nil {
+			utils.AssertEqual(t, "missing handler in route: /doe\n", fmt.Sprintf("%v", err))
+		}
+	}()
+	app.register("USE", "/doe")
+}
+
 func Test_Ensure_Router_Interface_Implementation(t *testing.T) {
 	var app interface{} = (*App)(nil)
 	_, ok := app.(Router)