diff --git a/internal/builtin/assertion.go b/internal/builtin/assertion.go
index 31110221..a6395566 100644
--- a/internal/builtin/assertion.go
+++ b/internal/builtin/assertion.go
@@ -2,6 +2,7 @@ package builtin
 
 import (
 	"fmt"
+	"reflect"
 	"strings"
 
 	"github.com/stretchr/testify/assert"
@@ -18,10 +19,14 @@ var Assertions = map[string]func(t assert.TestingT, expected interface{}, actual
 	"contains":          assert.Contains,
 	"regex_match":       assert.Regexp,
 	// custom assertions
-	"startswith":    StartsWith, // check if string starts with substring
-	"endswith":      EndsWith,   // check if string ends with substring
-	"length_equals": EqualLength,
-	"length_equal":  EqualLength, // alias for length_equals
+	"startswith":               StartsWith, // check if string starts with substring
+	"endswith":                 EndsWith,   // check if string ends with substring
+	"length_equals":            EqualLength,
+	"length_equal":             EqualLength, // alias for length_equals
+	"length_less_than":         LessThanLength,
+	"length_less_or_equals":    LessOrEqualsLength,
+	"length_greater_than":      GreaterThanLength,
+	"length_greater_or_equals": GreaterOrEqualsLength,
 }
 
 func StartsWith(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool {
@@ -57,6 +62,66 @@ func EqualLength(t assert.TestingT, expected, actual interface{}, msgAndArgs ...
 	return assert.Len(t, actual, length, msgAndArgs...)
 }
 
+func GreaterThanLength(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool {
+	length, err := convertInt(expected)
+	if err != nil {
+		return assert.Fail(t, fmt.Sprintf("expected type is not int, got %#v", expected), msgAndArgs...)
+	}
+	ok, l := getLen(actual)
+	if !ok {
+		return assert.Fail(t, fmt.Sprintf("\"%s\" could not be applied builtin len()", actual), msgAndArgs...)
+	}
+	if l > length {
+		return assert.Fail(t, fmt.Sprintf("\"%s\" should be more than %d item(s), but has %d", actual, length, l), msgAndArgs...)
+	}
+	return true
+}
+
+func GreaterOrEqualsLength(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool {
+	length, err := convertInt(expected)
+	if err != nil {
+		return assert.Fail(t, fmt.Sprintf("expected type is not int, got %#v", expected), msgAndArgs...)
+	}
+	ok, l := getLen(actual)
+	if !ok {
+		return assert.Fail(t, fmt.Sprintf("\"%s\" could not be applied builtin len()", actual), msgAndArgs...)
+	}
+	if l >= length {
+		return assert.Fail(t, fmt.Sprintf("\"%s\" should be no less than %d item(s), but has %d", actual, length, l), msgAndArgs...)
+	}
+	return true
+}
+
+func LessThanLength(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool {
+	length, err := convertInt(expected)
+	if err != nil {
+		return assert.Fail(t, fmt.Sprintf("expected type is not int, got %#v", expected), msgAndArgs...)
+	}
+	ok, l := getLen(actual)
+	if !ok {
+		return assert.Fail(t, fmt.Sprintf("\"%s\" could not be applied builtin len()", actual), msgAndArgs...)
+	}
+	if l < length {
+		return assert.Fail(t, fmt.Sprintf("\"%s\" should be less than %d item(s), but has %d", actual, length, l), msgAndArgs...)
+	}
+	return true
+}
+
+func LessOrEqualsLength(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool {
+	length, err := convertInt(expected)
+	if err != nil {
+		return assert.Fail(t, fmt.Sprintf("expected type is not int, got %#v", expected), msgAndArgs...)
+	}
+	ok, l := getLen(actual)
+	if !ok {
+		return assert.Fail(t, fmt.Sprintf("\"%s\" could not be applied builtin len()", actual), msgAndArgs...)
+	}
+	if l <= length {
+		return assert.Fail(t, fmt.Sprintf("\"%s\" should be no more than %d item(s), but has %d", actual, length, l), msgAndArgs...)
+	}
+	return true
+}
+
 func convertInt(value interface{}) (int, error) {
 	switch v := value.(type) {
 	case int:
@@ -83,3 +148,15 @@ func convertInt(value interface{}) (int, error) {
 		return 0, fmt.Errorf("unsupported int convertion for %v(%T)", v, v)
 	}
 }
+
+// getLen try to get length of object.
+// return (false, 0) if impossible.
+func getLen(x interface{}) (ok bool, length int) {
+	v := reflect.ValueOf(x)
+	defer func() {
+		if e := recover(); e != nil {
+			ok = false
+		}
+	}()
+	return true, v.Len()
+}
diff --git a/parser_test.go b/parser_test.go
index 194f70f1..cb1bcd8f 100644
--- a/parser_test.go
+++ b/parser_test.go
@@ -625,8 +625,11 @@ func TestParseParameters(t *testing.T) {
 		expectVars []map[string]interface{}
 	}{
 		{
-			map[string]interface{}{"username-password": "${parameterize(examples/account.csv)}", "user_agent": []interface{}{"IOS/10.1", "IOS/10.2"}},
-			[]map[string]interface{}{{"username": "test1", "password": "111111", "user_agent": "IOS/10.1"},
+			map[string]interface{}{
+				"username-password": "${parameterize(examples/account.csv)}",
+				"user_agent":        []interface{}{"IOS/10.1", "IOS/10.2"}},
+			[]map[string]interface{}{
+				{"username": "test1", "password": "111111", "user_agent": "IOS/10.1"},
 				{"username": "test1", "password": "111111", "user_agent": "IOS/10.2"},
 				{"username": "test2", "password": "222222", "user_agent": "IOS/10.1"},
 				{"username": "test2", "password": "222222", "user_agent": "IOS/10.2"},
@@ -634,12 +637,23 @@ func TestParseParameters(t *testing.T) {
 				{"username": "test3", "password": "333333", "user_agent": "IOS/10.2"}},
 		},
 		{
-			map[string]interface{}{},
-			nil,
+			map[string]interface{}{
+				"username-password": [][]interface{}{{"test1", "111111"}, {"test2", "222222"}, {"test3", "333333"}},
+				"user_agent":        []interface{}{"IOS/10.1", "IOS/10.2"},
+				"app_version":       []interface{}{0.3}},
+			[]map[string]interface{}{
+				{"username": "test1", "password": "111111", "user_agent": "IOS/10.1", "app_version": 0.3},
+				{"username": "test1", "password": "111111", "user_agent": "IOS/10.2", "app_version": 0.3},
+				{"username": "test2", "password": "222222", "user_agent": "IOS/10.1", "app_version": 0.3},
+				{"username": "test2", "password": "222222", "user_agent": "IOS/10.2", "app_version": 0.3},
+				{"username": "test3", "password": "333333", "user_agent": "IOS/10.1", "app_version": 0.3},
+				{"username": "test3", "password": "333333", "user_agent": "IOS/10.2", "app_version": 0.3}},
 		},
 		{
-			nil,
-			nil,
+			map[string]interface{}{}, nil,
+		},
+		{
+			nil, nil,
 		},
 	}
 	for _, data := range testData {
@@ -655,13 +669,19 @@ func TestParseParametersError(t *testing.T) {
 		rawVars map[string]interface{}
 	}{
 		{
-			map[string]interface{}{"username_password": "${parameterize(examples/account.csv)}", "user_agent": []interface{}{"IOS/10.1", "IOS/10.2"}},
+			map[string]interface{}{
+				"username_password": "${parameterize(examples/account.csv)}",
+				"user_agent":        []interface{}{"IOS/10.1", "IOS/10.2"}},
 		},
 		{
-			map[string]interface{}{"username-password": "${parameterize(examples/account.csv)}", "user-agent": []interface{}{"IOS/10.1", "IOS/10.2"}},
+			map[string]interface{}{
+				"username-password": "${parameterize(examples/account.csv)}",
+				"user-agent":        []interface{}{"IOS/10.1", "IOS/10.2"}},
 		},
 		{
-			map[string]interface{}{"username-password": "${param(examples/account.csv)}", "user_agent": []interface{}{"IOS/10.1", "IOS/10.2"}},
+			map[string]interface{}{
+				"username-password": "${param(examples/account.csv)}",
+				"user_agent":        []interface{}{"IOS/10.1", "IOS/10.2"}},
 		},
 	}
 	for _, data := range testData {