src/Context/Message/MessageContext.php
public function assertNoErrorMessages()
    {
        foreach ($this->getMessagesContainers('error') as $element) {
            // Some modules are inserted an empty container for errors before
            // they are arise. The "Clientside Validation" - one of them.
            $text = trim($element->getText());

            if ('' !== $text) {
                throw new \RuntimeException(sprintf(
                    'The page "%s" contains following error messages: "%s".',
                    self::$pageUrl,
                    $text
                ));
            }
        }

        /** @var NodeElement $formElement */
        foreach ($this->getSession()->getPage()->findAll('css', 'input, select, textarea') as $formElement) {
            if ($formElement->hasClass('error')) {
                throw new \Exception(sprintf(
                    'Element "#%s" has an error class.',
                    $formElement->getAttribute('id')
                ));
            }
        }
    }
public function assertNoErrorMessages()
    {
        foreach ($this->getMessagesContainers('error') as $element) {
            // Some modules are inserted an empty container for errors before
            // they are arise. The "Clientside Validation" - one of them.
            $text = trim($element->getText());

            if ('' !== $text) {
                throw new \RuntimeException(sprintf(
                    'The page "%s" contains following error messages: "%s".',
                    self::$pageUrl,
                    $text
                ));
            }
        }

        /** @var NodeElement $formElement */
        foreach ($this->getSession()->getPage()->findAll('css', 'input, select, textarea') as $formElement) {
            if ($formElement->hasClass('error')) {
                throw new \Exception(sprintf(
                    'Element "#%s" has an error class.',
                    $formElement->getAttribute('id')
                ));
            }
        }
    }
Check that the page have no error messages and fields - error classes.

@throws \RuntimeException
@throws \Exception

@Then /^(?:|I )should see no errors(?:| on the page)$/