How to know if the observer function have executed after an event?

Question

I am trying to observe an event. How can I debug or know if the observer function has been called? I am using the event "checkout_cart_add_product_complete" and trying to do something simple when a product is added to the cart. But nothing happen when I add the product. I would like to know if the function was reached. My "events.xml":

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
<event name="checkout_cart_add_product_complete">
    <observer name="send_order_tracy" instance="Tracy\ShippingMethod\Observer\SendOrderToTracy"/>
</event>
</config>

My observer class:

<?php

namespace Tracy\ShippingMethod\Observer;

class SendOrderToTracy implements \Magento\Framework\Event\ObserverInterface
{
    public function execute(\Magento\Framework\Event\Observer $observer)
    {
        debug_to_console("por la chuchaaa");
        //die('Observer Is called!');
    }

    function debug_to_console( $data ) {
        $output = $data;
        if ( is_array( $output ) )
            $output = implode( ',', $output);

        echo "<script>console.log( 'Debug Objects: " . $output . "' );</script>";
    }
}

Answer 1

You can use below code in your observer execute function like this-

public function execute(\Magento\Framework\Event\Observer $observer)
    {
       $writer = new \Zend\Log\Writer\Stream(BP.'/var/log/test.log'); // creates new log file named test.log in var/log folder
       $logger = new \Zend\Log\Logger();
       $logger->addWriter($writer);
       $logger->info("observer called"); // this will be print in test.log file

    }

For newer Magento2.4.X version :

$writer = new \Zend_Log_Writer_Stream(BP . '/var/log/test.log');
$logger = new \Zend_Log();
$logger->addWriter($writer);
$logger->info("---my custome message-----" );

it will create new log file named 'test.log' in var/log folder and it will print string 'observer called' in it if observer is called.

Answer 2

try to add this script on your debug_to_console function :

\Magento\Framework\App\ObjectManager::getInstance()
    ->get(\Psr\Log\LoggerInterface::class)->debug('observer function called');

it will write message to your log file, I don't remember what is exactly but you can find in these log file debug.log, system.log or exception.log just check one of them.

note : objectManager is not recommended way, but I write this just to debug and make sure your observer called. After you found it works just deleted this code part