<?php
/**
 * php-binary
 * A PHP library for parsing structured binary streams
 *
 * @package  php-binary
 * @author Damien Walsh <me@damow.net>
 */
namespace Binary\Validator;
use Binary\Exception\ValidatorException;

/**
 * Equal
 * Validator
 *
 * @since 1.0
 */
class Equal extends AbstractValidator
{
    public function validate($input)
    {
        if ($input != $this->desiredValue) {
            throw new ValidatorException(
                'Field value is ' . $input . '. ' .
                'Must be equal to ' .
                $this->desiredValue
            );
        }
    }
}

<?php
/**
 * php-binary
 * A PHP library for parsing structured binary streams
 *
 * @package  php-binary
 * @author Damien Walsh <me@damow.net>
 */
namespace Binary\Validator;

/**
 * Equal
 * Validator
 *
 * @since 1.0
 */
class Equal extends AbstractValidator
{
    public function validate($input)
    {
        if ($input != $this->desiredValue) {
            throw new \Exception('Fail!');
        }
    }
}

--- 
+++ 
@@ -7,6 +7,7 @@
  * @author Damien Walsh <me@damow.net>
  */
 namespace Binary\Validator;
+use Binary\Exception\ValidatorException;
 
 /**
  * Equal
@@ -19,7 +20,11 @@
     public function validate($input)
     {
         if ($input != $this->desiredValue) {
-            throw new \Exception('Fail!');
+            throw new ValidatorException(
+                'Field value is ' . $input . '. ' .
+                'Must be equal to ' .
+                $this->desiredValue
+            );
         }
     }
 }
Update validator to produce more detailed exception message.
