behat 3 - Using constructor breaks output - behat

Question

I followed the tutorial on http://docs.behat.org/en/latest/quick_intro_pt1.html.
But when I have implemented the feature and running behat it is said in the tutorial that I should get an error: "Fatal error: Class 'Shelf' not found."
I did not get that error. Only the output of the user story:
$ vendor/bin/behat
Feature: Product basket
In order to buy products
As a customer
I need to be able to put interesting products into a basket
Rules:
- VAT is 20%
- Delivery for basket under £10 is £3
- Delivery for basket over £10 is £2
class FeatureContext implements SnippetAcceptingContext
{
private $shelf;
private $basket;
public function __construct()
{
$this->shelf = new Shelf();
$this->basket = new Basket($this->shelf);
}
/**
* #Given there is a :product, which costs £:price
*/
public function thereIsAWhichCostsPs($product, $price)
{
$this->shelf->setProductPrice($product, floatval($price));
}
It looks like, when I am using a constructor this happening and the output of behat is just the user story but not the tests.
Even if I put an exit() in the function the exit() is not happening.
I have tried this with different projects in PHPStorm. It is always the same.
I am wondering how I could get the expectedt error: "Fatal error: Class 'Shelf' not found."
I am using behat 3.0.14: I have used composer to install it.