src/Utils/FormValueAssertion.php
public function checkable()
    {
        $this->restrictElements(['input' => ['radio', 'checkbox']]);

        if (!in_array($this->element->getAttribute('type'), ['radio', 'checkbox'])) {
            throw new \RuntimeException('Element cannot be checked.');
        }

        self::debug(['%s'], [$this->element->getOuterHtml()]);

        $this->assert($this->element->isChecked(), 'checked');
    }
public function checkable()
    {
        $this->restrictElements(['input' => ['radio', 'checkbox']]);

        if (!in_array($this->element->getAttribute('type'), ['radio', 'checkbox'])) {
            throw new \RuntimeException('Element cannot be checked.');
        }

        self::debug(['%s'], [$this->element->getOuterHtml()]);

        $this->assert($this->element->isChecked(), 'checked');
    }
Ensure that checkbox/radio button is checked.