assert_options
hodgman at ali dot com dot au said:
"Assertions should only be enabled during testing/development, and then disabled once your code reaches a production stage."
Assertions should _not_ be turned off in production code. Although it's common to do so, turning off assertions in production is a bad practice.
If your production code fails an assert, YOU WANT TO KNOW ABOUT IT. Asserts are a debugging tool, but you should not stop debugging your code just because it has gone into production.
Many people claim that removing asserts gives a performance benefit. In modern programming languages this simply isn't true. If you were doing an assert on something that is extremely slow/expensive to compute, you might consider turning that assert off. But in practice this really isn't how asserts are used.
There's a good discussion of this issue in the book The Pragmatic Programmer.
assert
(PHP 4, PHP 5)
assert — Prüft ab, ob eine Bedingung oder Abfrage FALSE ist
Beschreibung
int assert
( string|bool $assertion
)
assert() überprüft den übergebenen Parameter assertion und führt ein über die Funktion assert_options() definiertes Ereignis aus, falls die in assertion spezifizierte Bedingung FALSE ist.
Wird der Parameter assertion als String übergeben, so wird der String als PHP-Code interpretiert. Der Vorteil der Übergabe des Parameters assertion als Zeichenkette liegt darin, dass die ausgegebene Meldung die über assertion übergebene Zeichenkette enthält.
assert() sollte nur zum Debuggen des Codes und nicht in Produktionsumgebungen verwendet werden werden, beispielsweise zur Überprüfung von Eingaben.
Die Optionen für die assert() können über die Funktion assert_options() oder in den Einstellungen der .ini-Datei gesetzt werden.
Die Funktion assert_options() mit der ASSERT_CALLBACK Direktive ermöglicht eine Funktion anzugeben, die bei fehlender Überprüfung aufgerufen wird.
Callback-Funktionen in Zusammenhang mit assert() sind nützlich, um beispielsweise automatisierte Tests durchzuführen, da die Callback-Funktion über die Information verfügt, von welcher Stelle sie aufgerufen wurde.
Die Callback-Funktion wird mit drei Parametern aufgerufen. Der erste Parameter enthält den Namen des Scripts, in dem die Überprüfung statt fand, der zweite Parameter die Zeilennummer, und der dritte Paramter enthält die über assertion angegebene Bedingung.
Beispiel #1 Überprüfung mit benutzerdefinierter Funktion
<?php
// Active assert and make it quiet
assert_options (ASSERT_ACTIVE, 1);
assert_options (ASSERT_WARNING, 0);
assert_options (ASSERT_QUIET_EVAL, 1);
// Create a handler function
function my_assert_handler ($file, $line, $code) {
echo "<hr>Assertion Failed:
File '$file'<br>
Line '$line'<br>
Code '$code'<br><hr>";
}
// Set up the callback
assert_options (ASSERT_CALLBACK, 'my_assert_handler');
// Make an assertion that should fail
assert ('mysql_query ("")');
?>
add a note
User Contributed Notesassert
tom russo at gmail dot com
25-Dec-2006 12:25
25-Dec-2006 12:25
mail<at>aaron-mueller.de
13-Sep-2006 07:51
13-Sep-2006 07:51
Here is a simple demonstration of Design By Contract with PHP
<?php
assert_options(ASSERT_ACTIVE, 1);
assert_options(ASSERT_WARNING, 0);
assert_options(ASSERT_BAIL, 1);
assert_options(ASSERT_CALLBACK, 'dcb_callback');
function dcb_callback($script, $line, $message) {
echo "<h1>Condition failed!</h1><br />
Script: <strong>$script</strong><br />
Line: <strong>$line</strong><br />
Condition: <br /><pre>$message</pre>";
}
// Parameters
$a = 5;
$b = 'Simple DCB with PHP';
// Pre-Condition
assert('
is_integer($a) &&
($a > 0) &&
($a < 20) &&
is_string($b) &&
(strlen($b) > 5);
');
// Function
function combine($a, $b) {
return "Kombined: " . $b . $a;
}
$result = combine($a, $b);
// Post-Condition
assert('
is_string($result) &&
(strlen($result) > 0);
');
// All right, the Function works fine
var_dump($result);
?>
hodgman at ali dot com dot au
11-Aug-2006 01:45
11-Aug-2006 01:45
I dont agree with gk at proliberty dot com's statements below.
If you are constantly enabling assertions before each assertion, then you are removing the functionality provided by being able to turn off assertions in the first place.
Assertions should only be enabled during testing/development, and then disabled once your code reaches a production stage.
This means you should either leave disabling/enabling assertions up to the INI file, or let the entry point of the script decide.
If you need an assertion to be there in the final copy of the code, then you are using the wrong tool. Assertions are a tool for debugging only.
gk at proliberty dot com
27-Aug-2005 04:35
27-Aug-2005 04:35
If you expect your code to be able to work well with other code, then you should not make any assumptions about the current state of assert_options() flags, prior to calling assert(): other code may disable ASSERT_ACTIVE, without you knowing it - this would render assert() useless!
To avoid this, ALWAYS set assert_options() IMMEDIATELY before calling assert(), per the C++ paradigm for assertion usage:
In one C++ source file, you can define and undefine NDEBUG multiple times, each time followed by #include <cassert>, to enable or disable the assert macro multiple times in the same source file.
Here is how I workaround this issue in my PHP code:
//////////////////////////////////////////////////////////////////////
/// phpxAssertHandler_f
//////////////////////////////////////////////////////////////////////
/**
* @desc Handler which also sets up assert options if not being called as handler
Always fatal when assertion fails
Always make sure assertion is enabled
Cannot depend on other code not using assert or using its own assert handler!
USAGE:
// customize error level of assertion (php assert_options() only allows E_WARNING or nothing at all):
phpxAssertHandler_f(E_USER_NOTICE);
// control assertion active state: not dependent on anything another piece of code might do with ASSERT_ACTIVE
$GLOBALS['MY_ASSERT_ACTIVE']=false;
phpxAssertHandler_f(E_USER_NOTICE,$GLOBALS['MY_ASSERT_ACTIVE']);
// use alternate assertion callback function:
// NOTE: pass null as custom options parameter to use default options
// NOTE: pass no values for assert options parameter array elements to use default options
$GLOBALS['MY_ASSERT_ACTIVE']=false;
$GLOBALS['MY_ASSERT_CALLBACK']='myAssertCallback';
phpxAssertHandler_f(
null,
array(
0=>$GLOBALS['MY_ASSERT_ACTIVE'],
3=>$GLOBALS['MY_ASSERT_CALLBACK'],
)
);
* @param mixed = file or options
* @param line
* @param code
* @return void
*/
function phpxAssertHandler_f($file_or_custom_options=null, $line_or_assert_options=null, $code=null){
static $custom_options;
$debug = false;
if (is_null($code)){
// set default assert_options
$assert_options[]=1;//ASSERT_ACTIVE
$assert_options[]=0;//ASSERT_WARNING -
$assert_options[]=0;//ASSERT_QUIET_EVAL
$assert_options[]=__FUNCTION__;//ASSERT_CALLBACK
// set default custom_options
$custom_options[]=E_USER_ERROR;// error level
if (!is_null($line_or_assert_options)){
// assert_options are passed in
if (!is_array($line_or_assert_options)){
$line_or_assert_options=array($line_or_assert_options);
}
foreach ($line_or_assert_options as $i=>$assert_option){
if ($assert_option===true) $assert_option=1;
if ($assert_option===false) $assert_option=0;
$assert_options[$i]=$assert_option;
if($debug) echo ("assert_options[$i]=$assert_option\n");
}
}
if (!is_null($file_or_custom_options)){
// custom_options are passed in
if (!is_array($file_or_custom_options)){
$file_or_custom_options=array($file_or_custom_options);
}
foreach ($file_or_custom_options as $i=>$custom_option){
if ($custom_option===true) $custom_option=1;
if ($custom_option===false) $custom_option=0;
$custom_options[$i]=$custom_option;
if($debug) echo ("custom_options[$i]=$custom_option\n");
}
}
// set assert options
@assert_options (ASSERT_ACTIVE, $assert_options[0]);
@assert_options (ASSERT_WARNING, $assert_options[1]);
@assert_options (ASSERT_QUIET_EVAL, $assert_options[2]);
@assert_options (ASSERT_CALLBACK, $assert_options[3]);
} else {
// we are acting as a callback function
$file = $file_or_custom_options;
$line = $line_or_assert_options;
$msg="ASSERTION FAILED: $code";
phpxErrorHandler_f ($custom_options[0],$msg,$file,$line);
}
}//phpxAssertHandler_f()
Thomas
28-Mar-2005 05:56
28-Mar-2005 05:56
Another very good unit testing framework is SimpleTest, which can be found at http://www.lastcraft.com/simple_test.php
It has very good documentation, support for mock objects and tools for automating testing of entire web sites.
nyk at forumone dot com
27-Aug-2002 03:56
27-Aug-2002 03:56
Assertion is a useful debugging feature, but for building unit tests and automated regression tests you should seriously consider using the PHPtest in the PEAR archive (http://pear.php.net/package-info.php?pacid=38) that is based on the JUnit framework for Java. There is also another unit testing framework, also based on JUnit and also called PHPunit on SourceForge (http://sourceforge.net/projects/phpunit/). I believe it is an independent effort from that on PEAR.