testing error_log with PHPUnit

Question

I have this function I want to test looking like this:

class Logger {
  function error($msg){
    if (is_string($msg)){
      error_log($msg);
      die($msg);
    } elseif (is_object($msg)){
      error_log($msg.' '.$msg->getTraceAsString());
      die('exception');
    } else {
      var_dump($msg);
      die('error');
    }
  }

I want to test this function without logging the $msg. Is there a way to determine if error_log works without logging? I tried using setExpectedException but I wasn't able to catch the error and it kept logging.

Answer 1

The obvious answer is a simple alias/proxy-function that itself called error_log in the Logger class (which can be easily mocked, and checked to see what is set to it),

To actually test the native error_log function however (without a proxy in the original class), can be done with namespaces. The test would end up defined to be the same namespace as the original code, and then after the test class, add a function - in this case error_log() - but that function is also defined in the namespace - and so would be run in preference to the root-namespace-equivalent from the native functions.

Unfortunately, you can't do the same overriding with die (or its alias, exit). They are 'language constructs', and cannot be overridden like error_log can.

<?php
namespace abc;
use abc\Logger;

class ThreeTest extends \PHPUnit_Framework_TestCase
{
    public function setUp() { $this->l = new Logger(); }
    // test code to exercise 'abc\Logger'

}

// Now define a function, still inside the namespace '\abc'.
public function error_log($msg)
{
   // this will be called from abc\Logger::error
   // instead of the native error_log() function
   echo "ERR: $msg, ";
}

Answer 2

you can use a function-mocking framework like php-mock (there are others as well) to mock the call to error_log (and check whether it is called with your expected parameters).

Unfortunately you will not be able to use that for the die-construct as that is not a normal function but anlanguage construct.

I'd replace the die() with a 'throw new \Exception()' (or any other appropriate exception) as you can then

• test for the thrown exception and
• can decide in your programming whether execution shall be stopped on calling the logger or whether you want to go on by wrapping the call into a try/catch

But I'd also ask myself whether the execution has to stop when calling a logger