diff --git a/docs/language_specification.txt b/docs/language_specification.txt
deleted file mode 100644
index bfa71a2..0000000
--- a/docs/language_specification.txt
+++ /dev/null
@@ -1,86 +0,0 @@
-!true
-!=
->
-<
->=
-<=
-var five = 5;
-var conta_0_L3Tr4as = "Other Variable";
-var pi = 3.1415;
-var booleano = true;
-var booleanoFalso = false;
-var conta = five * pi;
-var contaMetada = (conta / 2) - 10;
-
-function saySomething(name) {
-    return "Said: " + name;
-}
-
-var println = function() {
-    return "Echo!!"
-}
-
-saySomething("Hello " + name);
-
-if (five > 10) {
-    saySomething("Ups");
-} elseif (five == 10) {
-    saySomething("Its same");
-} else {
-    saySomething("All fine");
-}
-
-var statusCode = [200, 300, 400];
-var otherArray = [function () {}, "testing", 123.23, {"hello":"world"}];
-
-if (statusCode[0] != 200) {
-    saySomething("200 status code");
-}
-
-var hashesResponse = {"nope":"an error happend", "ok":"everthing is ok"}
-
-for (index in statusCode) {
-	var item = statusCode[index];
-}
-
------------------
-* * * * * * * * *
-
-
-function add(x, y = 123) {
-    return x + y;
-}
-
-class testing {
-	public construct() {
-		this.testing();
-		this.do(10, 10);
-	}
-
-	public call() {
-	}
-
-	private testing() {
-		println("hello world");
-	}
-
-	protected do(x, y) {
-		return x + y;
-	}
-}
-
-var a = new testing();
-a.call();
-
-async {
-
-}
-
-* * * * * *
-
-Illegal or must be illegal
-
-
-var testing = function add() {
-    return "1";
-}
diff --git a/docs/todo.txt b/docs/todo.txt
deleted file mode 100644
index 6267ed2..0000000
--- a/docs/todo.txt
+++ /dev/null
@@ -1,9 +0,0 @@
-# Errors
-
-Case 1:
-for(var i = 0; i <= len(b)-1; b = b +1) { puts(b[i]); }
-
-Case 2:
-var a = "hello";
-if (a.type() == "STRING") { puts(a.split("")); }
-
diff --git a/evaluator/array_test.go b/evaluator/array_test.go
index 2f499f0..4399f57 100644
--- a/evaluator/array_test.go
+++ b/evaluator/array_test.go
@@ -1,6 +1,7 @@
 package evaluator
 
 import (
+	"fmt"
 	"ninja/object"
 	"testing"
 )
@@ -330,46 +331,53 @@ func TestArrayMethodWrongUsage(t *testing.T) {
 		input                string
 		expectedErrorMessage string
 	}{
+		{
+			`[].type(1)`,
+			"TypeError: array.type() takes exactly 0 argument (1 given)",
+		},
 		{
 			`[].join([])`,
-			"array.join expect first argument be string. Got: ARRAY",
+			"TypeError: array.join() expected argument #1 to be `STRING` got `ARRAY`",
 		},
 		{
 			`[1].length(1)`,
-			"array.length not accept any arguments. got: [1]",
+			"TypeError: array.length() takes exactly 0 argument (1 given)",
 		},
 		{
 			`[].join()`,
-			"array.join expect exactly 1 argument. Got: 0",
+			"TypeError: array.join() takes exactly 1 argument (0 given)",
 		},
 		{
 			`[].push()`,
-			"array.push expect exactly 1 argument. Got: 0",
+			"TypeError: array.push() takes a minimum 1 arguments (0 given)",
 		},
 		{
 			`[1].pop(1)`,
-			"array.pop expect exactly 0 argument. Got: 1",
+			"TypeError: array.pop() takes exactly 0 argument (1 given)",
 		},
 		{
 			`[1].shift(1)`,
-			"array.shift expect exactly 0 argument. Got: 1",
+			"TypeError: array.shift() takes exactly 0 argument (1 given)",
 		},
 		{
 			`[1].slice(1, 2, 3)`,
-			`array.slice(start, offset) expected at least 1 argument and at max 2 arguments. Got: [1, 2, 3]`,
+			`TypeError: array.push() takes at least 1 arguments at most 2 (3 given)`,
 		},
 	}
 
-	for _, tt := range tests {
-		evaluated := testEval(tt.input, t)
+	for i, tt := range tests {
+		t.Run(fmt.Sprintf("TestArrayMethodWrongUsage[%d]", i), func(t *testing.T) {
+			evaluated := testEval(tt.input, t)
 
-		errObj, ok := evaluated.(*object.Error)
-		if !ok {
-			t.Fatalf("no error object returned. got=%T(%+v)", evaluated, evaluated)
-		}
+			errObj, ok := evaluated.(*object.Error)
+			if !ok {
+				t.Fatalf("no error object returned. got=%T(%+v)", evaluated, evaluated)
+			}
+
+			if errObj.Message != tt.expectedErrorMessage {
+				t.Errorf("erro expected \"%s\". Got: %s", tt.expectedErrorMessage, errObj.Message)
+			}
+		})
 
-		if errObj.Message != tt.expectedErrorMessage {
-			t.Errorf("erro expected \"%s\". Got: %s", tt.expectedErrorMessage, errObj.Message)
-		}
 	}
 }
diff --git a/object/array.go b/object/array.go
index 2f81fc1..86945c1 100644
--- a/object/array.go
+++ b/object/array.go
@@ -27,16 +27,26 @@ func (ao *Array) Inspect() string {
 func (s *Array) Call(objectCall *ast.ObjectCall, method string, env *Environment, args ...Object) Object {
 	switch method {
 	case "type":
-		if len(args) > 0 {
-			argStr := InspectObject(args...)
-			return NewErrorFormat("method type not accept any arguments. got: %s", argStr)
+		err := Check(
+			"array.type", args,
+			ExactArgs(0),
+		)
+
+		if err != nil {
+			return NewError(err.Error())
 		}
+
 		return &String{Value: ARRAY_OBJ}
 	case "length":
-		if len(args) > 0 {
-			argStr := InspectObject(args...)
-			return NewErrorFormat("array.length not accept any arguments. got: %s", argStr)
+		err := Check(
+			"array.length", args,
+			ExactArgs(0),
+		)
+
+		if err != nil {
+			return NewError(err.Error())
 		}
+
 		return &Integer{Value: int64(len(s.Elements))}
 	case "join":
 		return arrayJoin(s.Elements, args...)
@@ -72,15 +82,19 @@ func (s *Array) Call(objectCall *ast.ObjectCall, method string, env *Environment
 }
 
 func arrayJoin(elements []Object, args ...Object) Object {
-	if len(args) != 1 {
-		return NewErrorFormat("array.join expect exactly 1 argument. Got: %d", len(args))
-	}
 
-	joinArgument, ok := args[0].(*String)
-	if !ok {
-		return NewErrorFormat("array.join expect first argument be string. Got: %s", args[0].Type())
+	err := Check(
+		"array.join", args,
+		ExactArgs(1),
+		WithTypes(STRING_OBJ),
+	)
+
+	if err != nil {
+		return NewError(err.Error())
 	}
 
+	joinArgument, _ := args[0].(*String)
+
 	var out bytes.Buffer
 	elementsString := []string{}
 	for _, el := range elements {
@@ -125,8 +139,13 @@ func arrayJoin(elements []Object, args ...Object) Object {
 }
 
 func arrayPush(elements []Object, args ...Object) Object {
-	if len(args) <= 0 {
-		return NewErrorFormat("array.push expect exactly 1 argument. Got: %d", len(args))
+	err := Check(
+		"array.push", args,
+		MinimumArgs(1),
+	)
+
+	if err != nil {
+		return NewError(err.Error())
 	}
 
 	arr := &Array{Elements: elements}
@@ -139,8 +158,13 @@ func arrayPush(elements []Object, args ...Object) Object {
 }
 
 func arrayPop(elements []Object, args ...Object) (popValue Object, newArray Object) {
-	if len(args) > 0 {
-		return NewErrorFormat("array.pop expect exactly 0 argument. Got: %d", len(args)), nil
+	err := Check(
+		"array.pop", args,
+		ExactArgs(0),
+	)
+
+	if err != nil {
+		return NewError(err.Error()), nil
 	}
 
 	if len(elements) <= 0 {
@@ -151,6 +175,15 @@ func arrayPop(elements []Object, args ...Object) (popValue Object, newArray Obje
 }
 
 func arrayShift(elements []Object, args ...Object) (shiftValue Object, newArray Object) {
+	err := Check(
+		"array.shift", args,
+		ExactArgs(0),
+	)
+
+	if err != nil {
+		return NewError(err.Error()), nil
+	}
+
 	if len(args) > 0 {
 		return NewErrorFormat("array.shift expect exactly 0 argument. Got: %d", len(args)), nil
 	}
@@ -162,14 +195,17 @@ func arrayShift(elements []Object, args ...Object) (shiftValue Object, newArray
 }
 
 func arraySlice(elements []Object, args ...Object) Object {
-	if len(args) <= 0 || len(args) >= 3 {
-		return NewErrorFormat("array.slice(start, offset) expected at least 1 argument and at max 2 arguments. Got: %s", InspectObject(args...))
+	err := Check(
+		"array.push", args,
+		RangeOfArgs(1, 2),
+		WithTypes(INTEGER_OBJ, INTEGER_OBJ),
+	)
+
+	if err != nil {
+		return NewError(err.Error())
 	}
 
-	start, ok := args[0].(*Integer)
-	if !ok {
-		return NewErrorFormat("array.slice(start, offset) first argument must be integer. Got: %s", args[0].Inspect())
-	}
+	start, _ := args[0].(*Integer)
 
 	maxLength := int64(len(elements))
 	offset := maxLength
diff --git a/typing/typing.go b/object/typing.go
similarity index 73%
rename from typing/typing.go
rename to object/typing.go
index 8e6c18c..6054d9c 100644
--- a/typing/typing.go
+++ b/object/typing.go
@@ -1,14 +1,13 @@
-package typing
+package object
 
 import (
 	"fmt"
-	"ninja/object"
 	"strings"
 )
 
-type CheckFunc func(name string, args []object.Object) error
+type CheckFunc func(name string, args []Object) error
 
-func Check(name string, args []object.Object, checks ...CheckFunc) error {
+func Check(name string, args []Object, checks ...CheckFunc) error {
 	for _, check := range checks {
 		if err := check(name, args); err != nil {
 			return err
@@ -18,7 +17,7 @@ func Check(name string, args []object.Object, checks ...CheckFunc) error {
 }
 
 func ExactArgs(n int) CheckFunc {
-	return func(name string, args []object.Object) error {
+	return func(name string, args []Object) error {
 		if len(args) != n {
 			return fmt.Errorf(
 				"TypeError: %s() takes exactly %d argument (%d given)",
@@ -29,7 +28,7 @@ func ExactArgs(n int) CheckFunc {
 	}
 }
 func MinimumArgs(n int) CheckFunc {
-	return func(name string, args []object.Object) error {
+	return func(name string, args []Object) error {
 		if len(args) < n {
 			return fmt.Errorf(
 				"TypeError: %s() takes a minimum %d arguments (%d given)",
@@ -40,7 +39,7 @@ func MinimumArgs(n int) CheckFunc {
 	}
 }
 func RangeOfArgs(n, m int) CheckFunc {
-	return func(name string, args []object.Object) error {
+	return func(name string, args []Object) error {
 		if len(args) < n || len(args) > m {
 			return fmt.Errorf(
 				"TypeError: %s() takes at least %d arguments at most %d (%d given)",
@@ -50,8 +49,8 @@ func RangeOfArgs(n, m int) CheckFunc {
 		return nil
 	}
 }
-func WithTypes(types ...object.ObjectType) CheckFunc {
-	return func(name string, args []object.Object) error {
+func WithTypes(types ...ObjectType) CheckFunc {
+	return func(name string, args []Object) error {
 		for i, t := range types {
 			if i < len(args) && args[i].Type() != t {
 				return fmt.Errorf(
@@ -64,8 +63,8 @@ func WithTypes(types ...object.ObjectType) CheckFunc {
 	}
 }
 
-func OneOfType(types ...object.ObjectType) CheckFunc {
-	return func(name string, args []object.Object) error {
+func OneOfType(types ...ObjectType) CheckFunc {
+	return func(name string, args []Object) error {
 		for _, vt := range types {
 			for _, va := range args {
 				if va.Type() == vt {
diff --git a/stdlib/args.go b/stdlib/args.go
index 859aa67..cfdbe0c 100644
--- a/stdlib/args.go
+++ b/stdlib/args.go
@@ -2,14 +2,13 @@ package stdlib
 
 import (
 	"ninja/object"
-	"ninja/typing"
 )
 
 func Args(args ...object.Object) object.Object {
 
-	err := typing.Check(
+	err := object.Check(
 		"args", args,
-		typing.ExactArgs(0),
+		object.ExactArgs(0),
 	)
 
 	if err != nil {
diff --git a/stdlib/first.go b/stdlib/first.go
index 3097fa5..ffcdef4 100644
--- a/stdlib/first.go
+++ b/stdlib/first.go
@@ -2,16 +2,15 @@ package stdlib
 
 import (
 	"ninja/object"
-	"ninja/typing"
 )
 
 func First(args ...object.Object) object.Object {
 
-	err := typing.Check(
+	err := object.Check(
 		"first", args,
-		typing.ExactArgs(1),
-		typing.WithTypes(object.ARRAY_OBJ),
-	);
+		object.ExactArgs(1),
+		object.WithTypes(object.ARRAY_OBJ),
+	)
 
 	if err != nil {
 		return object.NewError(err.Error())
diff --git a/stdlib/last.go b/stdlib/last.go
index 4ee6433..c7dd30d 100644
--- a/stdlib/last.go
+++ b/stdlib/last.go
@@ -2,15 +2,14 @@ package stdlib
 
 import (
 	"ninja/object"
-	"ninja/typing"
 )
 
 func Last(args ...object.Object) object.Object {
 
-	err := typing.Check(
+	err := object.Check(
 		"last", args,
-		typing.ExactArgs(1),
-		typing.WithTypes(object.ARRAY_OBJ),
+		object.ExactArgs(1),
+		object.WithTypes(object.ARRAY_OBJ),
 	)
 
 	if err != nil {
diff --git a/stdlib/len.go b/stdlib/len.go
index 5a74753..789bef3 100644
--- a/stdlib/len.go
+++ b/stdlib/len.go
@@ -2,15 +2,14 @@ package stdlib
 
 import (
 	"ninja/object"
-	"ninja/typing"
 )
 
 func Len(args ...object.Object) object.Object {
 
-	err := typing.Check(
+	err := object.Check(
 		"len", args,
-		typing.ExactArgs(1),
-		typing.OneOfType(object.ARRAY_OBJ, object.STRING_OBJ),
+		object.ExactArgs(1),
+		object.OneOfType(object.ARRAY_OBJ, object.STRING_OBJ),
 	)
 
 	if err != nil {
diff --git a/stdlib/push.go b/stdlib/push.go
index 52d590c..d332ea9 100644
--- a/stdlib/push.go
+++ b/stdlib/push.go
@@ -2,15 +2,14 @@ package stdlib
 
 import (
 	"ninja/object"
-	"ninja/typing"
 )
 
 func Push(args ...object.Object) object.Object {
 
-	err := typing.Check(
+	err := object.Check(
 		"push", args,
-		typing.ExactArgs(2),
-		typing.WithTypes(object.ARRAY_OBJ),
+		object.ExactArgs(2),
+		object.WithTypes(object.ARRAY_OBJ),
 	)
 
 	if err != nil {
diff --git a/stdlib/rand.go b/stdlib/rand.go
index f8c146b..08072f4 100644
--- a/stdlib/rand.go
+++ b/stdlib/rand.go
@@ -3,13 +3,12 @@ package stdlib
 import (
 	"math/rand"
 	"ninja/object"
-	"ninja/typing"
 )
 
 func Rand(args ...object.Object) object.Object {
-	err := typing.Check(
+	err := object.Check(
 		"rand", args,
-		typing.ExactArgs(0),
+		object.ExactArgs(0),
 	)
 
 	if err != nil {
diff --git a/stdlib/rest.go b/stdlib/rest.go
index 90a1fc0..fbeba35 100644
--- a/stdlib/rest.go
+++ b/stdlib/rest.go
@@ -2,15 +2,14 @@ package stdlib
 
 import (
 	"ninja/object"
-	"ninja/typing"
 )
 
 func Rest(args ...object.Object) object.Object {
 
-	err := typing.Check(
+	err := object.Check(
 		"first", args,
-		typing.ExactArgs(1),
-		typing.WithTypes(object.ARRAY_OBJ),
+		object.ExactArgs(1),
+		object.WithTypes(object.ARRAY_OBJ),
 	)
 
 	if err != nil {
diff --git a/stdlib/time.go b/stdlib/time.go
index faffb96..4c5f25f 100644
--- a/stdlib/time.go
+++ b/stdlib/time.go
@@ -2,14 +2,13 @@ package stdlib
 
 import (
 	"ninja/object"
-	"ninja/typing"
 	"time"
 )
 
 func Time(args ...object.Object) object.Object {
-	err := typing.Check(
+	err := object.Check(
 		"first", args,
-		typing.ExactArgs(0),
+		object.ExactArgs(0),
 	)
 
 	if err != nil {