To run a php file in a browser from your module, you need to temporarily disable the .htaccess file in your app folder.
For example, rename it to .htaccess2.
Then you can browse the file in your browser like this:
http://domain.com/app/code/{vendor}/{module}/Cron/Yourfile.php
Just don't forget to return the .htaccess file back to normal after debugging.
EDIT
You can test functions by calling your file through browser like this:
http://domain.com/path/to/cron/file/?function=testFunction
And in your cron php file, you can make a switch statement to call your functions like this:
switch($_GET['function']) {
case 'testFunction':
testFunction();
}
function testFunction() {
echo 'test';
// your cron logic
}
... //other functions
Although for debugging purposes, maybe you could use Magento's log functions to debug your problem.
See this question for more info: Magento 2: Replacement for Mage::log method?.