Yii 2 Captcha - verifyCode invalid

Yii 2.0 General Discussions
1

Controller:




'captcha' => [

                'class' => 'yii\captcha\CaptchaAction',

                'fixedVerifyCode' => YII_ENV_TEST ? 'testme' : null,

            ],

Model:




public $verifyCode;


['verifyCode', 'captcha']

View:




<?= $form->field($model, 'verifyCode')->widget(Captcha::className()) ?>

But verifyCode always invalid. Why?