I've a simple application, say it has some classes and an "extra" one that handles database requests. Currently i'm creating the database object everytime the app is used, but in some cases there's no need for a database connection. I'm doing it like this (PHP btw):
$db = new Database();
$foo = new Foo($db); // passing the db
But sometimes the $foo object does not need db access, as only methods without database actions are called. So my question is: What's the professional way to handle situations like this / how to create the db connection/object only when needed ?
My goal is to avoid unnecessary database connections.
Note: Although the direct answer to ops question, "when can I only create / connect to the database when required and not on every request" is inject it when you need it, simply saying that is not helpful. I'm explaining here how you actually go about that correctly, as there really isn't a lot of useful information out there in a non-specific-framework context to help in this regard.
Updated: The 'old' answer to this question can be see below. This encouraged the service locator pattern which is very controversial and to many an 'anti-pattern'. New answer added with what I've learned from researching. Please read the old answer first to see how this progressed.
New Answer
After using pimple for a while, I learned much about how it works, and how it's not actually that amazing after all. It's still pretty cool, but the reason it's only 80 lines of code is because it basically allows the creation of an array of closures. Pimple is used a lot as a service locator (because it's so limited in what it can actually do), and this is an "anti-pattern".
Firstly, what is a service locator?
The service locator pattern is a design pattern used in software development to encapsulate the processes involved in obtaining a service with a strong abstraction layer. This pattern uses a central registry known as the "service locator" which on request returns the information necessary to perform a certain task.
I was creating pimple in the bootstrap, defining dependencies, and then passing this container to each and every single class I instantiated.
Why is a service locator bad?
What's the problem with this you say? The main problem is that this approach hides dependencies from the class. So if a developer is coming to update this class and they haven't seen it before, they're going to see a container object containing an unknown amount of objects. Also, testing this class is going to be a bit of a nightmare.
Why did I do this originally? Because I thought that after the controller is where you start doing your dependency injection. This is wrong. You start it straight away at the controller level.
If this is how things work in my application:
Front Controller --> Bootstrap --> Router --> Controller/Method --> Model [Services|Domain Objects|Mappers] --> Controller --> View --> Template
...then the dependency injection container should start working right away at the first controller level.
So really, if I were to still use pimple, I would be defining what controllers are going to be created, and what they need. So you would inject the view and anything from the model layer into the controller so it can use it. This is Inversion Of Control and makes testing much easier. From the Aurn wiki, (which I'll talk about soon):
In real life you wouldn't build a house by transporting the entire hardware store (hopefully) to the construction site so you can access any parts you need. Instead, the foreman (__construct()) asks for the specific parts that will be needed (Door and Window) and goes about procuring them. Your objects should function in the same way; they should ask only for the specific dependencies required to do their jobs. Giving the House access to the entire hardware store is at best poor OOP style and at worst a maintainability nightmare. - From the Auryn Wiki
Enter Auryn
On that note, I'd like to introduce you to something brilliant called Auryn, written by Rdlowrey that I was introduced to over the weekend.
Auryn 'auto-wires' class dependencies based on the class constructor signature. What this means that, for each class requested, Auryn finds it, figures out what it needs in the constructor, creates what it needs first and then creates an instance of the class you asked for originally. Here's how it works:
The Provider recursively instantiates class dependencies based on the parameter type-hints specified in their constructor method signatures.
...and if you know anything about PHP's reflection, you'll know some people call it 'slow'. So here's what Auryn does about that:
You may have heard that "reflection is slow". Let's clear something up: anything can be "too slow" if you're doing it wrong. Reflection is an order of magnitude faster than disk access and several orders of magnitude faster than retrieving information (for example) from a remote database. Additionally, each reflection offers the opportunity to cache the results if you're worried about speed. Auryn caches any reflections it generates to minimize the potential performance impact.
So now we've skipped the "reflection is slow" argument, here's how I've been using it.
How I use Auryn
I make Auryn part of my autoloader. This is so that when a class is asked for, Auryn can go away and read the class and it's dependencies, and it's dependencies' dependencies (etc), and return them all into the class for instantiation. I create the Auyrn object.
$injector = new \Auryn\Provider(new \Auryn\ReflectionPool);
I use a Database Interface as a requirement in the constructor of my database class. So I tell Auryn which concrete implementation to use (this is the part you change if you want to instantiate a different type of database, at a single point in your code, and it'll all still work).
$injector->alias('Library\Database\DatabaseInterface', 'Library\Database\MySQL');
If I wanted to change to MongoDB and I'd written a class for it, I'd simple change Library\Database\MySQL to Library\Database\MongoDB.
Then, I pass the $injector into my router, and when creating the controller / method, this is where the dependencies are automatically resolved.
public function dispatch($injector)
{
// Make sure file / controller exists
// Make sure method called exists
// etc...
// Create the controller with it's required dependencies
$class = $injector->make($controller);
// Call the method (action) in the controller
$class->$action();
}
Finally, answer OP's question
Okay, so using this technique, let's say you have the User controller which requires the User Service (let's say UserModel) which requires Database access.
class UserController
{
protected $userModel;
public function __construct(Model\UserModel $userModel)
{
$this->userModel = $userModel;
}
}
class UserModel
{
protected $db;
public function __construct(Library\DatabaseInterface $db)
{
$this->db = $db;
}
}
If you use the code in the router, Auryn will do the following:
Create the Library\DatabaseInterface, using MySQL as the concrete class (alias'd in the boostrap)
Create the 'UserModel' with the previously created Database injected into it
Create the UserController with the previously created UserModel injected into it
That's the recursion right there, and this is the 'auto-wiring' I was talking about earlier. And this solves OPs problem, because only when the class hierarchy contains the database object as a constructor requirement is the object insantiated, not upon every request.
Also, each class has exactly the requirements they need to function in the constructor, so there are no hidden dependencies like there were with the service locator pattern.
RE: How to make it so that the connect method is called when required. This is really simple.
Make sure that in the constructor of your Database class, you don't instantiate the object, you just pass in it's settings (host, dbname, user, password).
Have a connect method which actually performs the new PDO() object, using the classes' settings.
class MySQL implements DatabaseInterface
{
private $host;
// ...
public function __construct($host, $db, $user, $pass)
{
$this->host = $host;
// etc
}
public function connect()
{
// Return new PDO object with $this->host, $this->db etc
}
}
So now, every class you pass the database to will have this object, but will not have the connection yet because connect() hasn't been called.
In the relevant model which has access to the Database class, you call $this->db->connect(); and then continue with what you want to do.
In essence, you still pass your database object to the classes that require it, using the methods I have described previously, but to decide when to perform the connection on a method-by-method basis, you just run the connect method in the required one. No you don't need a singleton. You just tell it when to connect when you want it to, and it doesn't when you don't tell it to connect.
Old Answer
I'm going to explain a little more in-depth about Dependency Injection Containers, and how they can may help your situation. Note: Understanding the principles of 'MVC' will help significantly here.
The Problem
You want to create some objects, but only certain ones need access to the database. What you're currently doing is creating the database object on each request, which is totally unnecessary, and also totally common before using things like DiC containers.
Two Example Objects
Here's an example of two objects that you may want to create. One needs database access, another doesn't need database access.
/**
* #note: This class requires database access
*/
class User
{
private $database;
// Note you require the *interface* here, so that the database type
// can be switched in the container and this will still work :)
public function __construct(DatabaseInterface $database)
{
$this->database = $database;
}
}
/**
* #note This class doesn't require database access
*/
class Logger
{
// It doesn't matter what this one does, it just doesn't need DB access
public function __construct() { }
}
So, what's the best way to create these objects and handle their relevant dependencies, and also pass in a database object only to the relevant class? Well, lucky for us, these two work together in harmony when using a Dependency Injection Container.
Enter Pimple
Pimple is a really cool dependency injection container (by the makers of the Symfony2 framework) that utilises PHP 5.3+'s closures.
The way that pimple does it is really cool - the object you want isn't instantiated until you ask for it directly. So you can set up a load of new objects, but until you ask for them, they aren't created!
Here's a really simple pimple example, that you create in your boostrap:
// Create the container
$container = new Pimple();
// Create the database - note this isn't *actually* created until you call for it
$container['datastore'] = function() {
return new Database('host','db','user','pass');
};
Then, you add your User object and your Logger object here.
// Create user object with database requirement
// See how we're passing on the container, so we can use $container['datastore']?
$container['User'] = function($container) {
return new User($container['datastore']);
};
// And your logger that doesn't need anything
$container['Logger'] = function() {
return new Logger();
};
Awesome! So.. how do I actually use the $container object?
Good question! So you've already created the $container object in your bootstrap and set up the objects and their required dependencies. In your routing mechanism, you pass the container to your controller.
Note: example rudimentary code
router->route('controller', 'method', $container);
In your controller, you access the $container parameter passed in, and when you ask for the user object from it, you get back a new User object (factory-style), with the database object already injected!
class HomeController extends Controller
{
/**
* I'm guessing 'index' is your default action called
*
* #route /home/index
* #note Dependant on .htaccess / routing mechanism
*/
public function index($container)
{
// So, I want a new User object with database access
$user = $container['User'];
// Say whaaat?! That's it? .. Yep. That's it.
}
}
What you've solved
So, you've now killed multiple birds (not just two) with one stone.
Creating a DB object on each request - Not any more! It's only created when you ask for it because of the closures Pimple uses
Removing 'new' keywords from your controller - Yep, that's right. You've handed this responsibility over to the container.
Note: Before I continue, I want to point out how significant bullet point two is. Without this container, let's say you created 50 user objects throughout your application. Then one day, you want to add a new parameter. OMG - you now need to go through your whole application and add this parameter to every new User(). However, with the DiC - if you're using $container['user'] everywhere, you just add this third param to the container once, and that's it. Yes, that totally is awesome.
The ability to switch out databases - You heard me, the whole point of this is that if you wanted to change from MySQL to PostgreSQL - you change the code in your container to return a new different type of database you've coded, and as long as it all returns the same sort of stuff, that's it! The ability to swap out concrete implementations that everyone always harps on about.
The Important Part
This is one way of using the container, and it's just a start. There are many ways to make this better - for example, instead of handing the container over to every method, you could use reflection / some sort of mapping to decide what parts of the container are required. Automate this and you're golden.
I hope you found this useful. The way I've done it here has at least cut significant amounts of development time for me, and it's good fun to boot!
This is approximately what I use.
class Database {
protected static $connection;
// this could be public if you wanted to be able to get at the core database
// set the class variable if it hasn't been done and return it
protected function getConnection(){
if (!isset(self::$connection)){
self::$connection = new mysqli($args);
}
return self::$connection;
}
// proxy property get to contained object
public function __get($property){
return $this->getConnection()->__get($property);
}
// proxy property set to contained object
public function __set($property, $value){
$this->getConnection()->__set($property, $value);
}
// proxy method calls to the contained object
public function __call($method, $args){
return call_user_func_array(array($this->getConnection(), $method), $args);
}
// proxy static method calls to the contained object
public function __callStatic($method, $args){
$connClass = get_class($this->getConnection());
return call_user_func_array(array($connClass, $method), $args);
}
}
Note it only works if there is a single database in play. If you wanted multiple different databases it would be possible to extend this but beware of late static binding in the getConnection method.
Here is an example of a simple approach:
class Database {
public $connection = null ;
public function __construct($autosetup = false){
if ($autosetup){
$this->setConnection() ;
}
}
public function getProducts(){//Move it to another class if you wish
$this->query($sql_to_get_products);
}
public function query($sql) {
if (!$connection || !$connection->ping()){
$this->setupConnection() ;
}
return $this->connection->query($sql);
}
public function setConnection(){
$this->connection = new MySQLi($a, $b, $c, $d) ;
}
public function connectionAvailable(){
return ($connection && $connection->ping()) ;
}
}
Look into using a dependency injection container, something like Pimple would be nice place to start. With a dependency injection container you 'teach' the container how to create the objects in your application, they're not instantiated until you ask for them. With Pimple, you can configure a resource to be shared so that it's only ever instantiated once during the request no matter how often you ask the container for it.
You can setup your classes to accept the container in their constructor or use a setter method to inject into your class.
A simplified example could look like this:
<?php
// somewhere in your application bootstrap
$container = new Pimple();
$container['db'] = $container->share(
function ($c) {
return new Database();
}
);
// somewhere else in your application
$foo = new Foo($container);
// somewhere in the Foo class definition
$bar = $this->container['db']->getBars();
Hope it helps.
You got some great answers already, with the majority concentrating on the aspect of injecting dependencies (which is a good thing), and only creating objects on demand.
The other aspect is the more important one: Do not put code that does any heavy work into your constructors. In case of a database object, this means: Do not connect to the database inside the constructor.
Why is this more important? Because not creating a database object because the using object also gets not created is no real optimization if the using object gets always created, but does not always run queries.
Creating an object in PHP is reasonable fast. The class code usually is available in the opcode cache, so it only triggers a call to the autoloader and then allocates some bytes in memory for the objects' properties. The constructor will run after that. If the only thing it does is copying the constructor parameters to local property variables, this is even optimized by PHP with "copy-on-write" references. So there is no real benefit if this object does not get created in the first place, if you cannot avoid it. If you can: even better.
I come from the world of Java. Java is resident in memory accross stateless HTML requests. PHP is not. That is a whole different story - and what I like about PHP.
I simply use:
$conn = #pg_connect(DBConnection);
the DBConnection is a definition containing the information about the host etc..
The # assures that the current connection is used or a new one is created. How can I do it more easily?
The data how to connect to the database is stable. The connection itself might be recreated during a request. Why should I program better then the people of PHP and recreate the #? They did that for the PHP community, let's use it.
By the way, never put heavy objects in a constructor and never let the constructor do some heavy job nor let it happen that an exception can be thrown during construction of an object. You might have an unfinished object resident in your memory. An init-method is to be preferred. I agree on that with Henrique Barcelos.
This is the way I am using mysqli. Database object behaves the same as mysqli object, can add my own methods or override existing ones, and the only difference is that the actual connection to database is not established when you create the object but on first call to method or property that needs the connection.
class Database {
private $arguments = array();
private $link = null;
public function __construct() {
$this->arguments = func_get_args();
}
public function __call( $method, $arguments ) {
return call_user_func_array( array( $this->link(), $method ), $arguments );
}
public function __get( $property ) {
return $this->link()->$property;
}
public function __set( $property, $value ){
$this->link()->$property = $value;
}
private function connect() {
$this->link = call_user_func_array( 'mysqli_connect', $this->arguments );
}
private function link() {
if ( $this->link === null ) $this->connect();
return $this->link;
}
}
Another way to achieve the same behavior is with use of mysqli_init() and mysqli_real_connect() methods, constructor initializes the object with mysqli_init(), and when you need a real connection the mysqli_real_connect() method is used.
class Database {
private $arguments = array();
public function __construct() {
$this->arguments = array_merge( array( 'link' => mysqli_init() ), func_get_args() );
}
public function __call( $method, $arguments ) {
return call_user_func_array( array( $this->link(), $method ), $arguments );
}
public function __get( $property ) {
return $this->link()->$property;
}
public function __set( $property, $value ) {
$this->link()->$property = $value;
}
private function connect() {
call_user_func_array( 'mysqli_real_connect', $this->arguments );
}
private function link() {
if ( !#$this->arguments['link']->thread_id ) $this->connect();
return $this->arguments['link'];
}
}
I tested memory consumption for both approaches and got quite unexpected results, the second approach uses less resources when connects to database and executes queries.
interface IDatabase {
function connect();
}
class Database implements IDatabase
{
private $db_type;
private $db_host;
private $db_name;
private $db_user;
private $db_pass;
private $connection = null;
public function __construct($db_type, $db_host, $db_name, $db_user, $db_pass)
{
$this->db_type = $db_type;
$this->db_host = $db_host;
$this->db_name = $db_name;
$this->db_user = $db_user;
$this->db_pass = $db_pass;
}
public function connect()
{
if ($this->connection === null) {
try {
$this->connection = new PDO($this->db_type.':host='.$this->db_host.';dbname='.$this->db_name, $this->db_user, $this->db_pass);
$this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
return $this->connection;
} catch (PDOException $e) {
return $e;
}
} else {
return $this->connection;
}
}
}
How about this? In connect(), check if a connection has already been established, if yes, return it, if not, create it and return it. This will prevent you from having TOO many connections open. Let's say, in your controller action, you want to call two methods of UserRepository (that depends on the Database), getUsers() and getBlockedUsers(), if you call these methods, connect() will be called in each one of them, with this check in place it will return the already existing instance.
You could use an singleton pattern to achive this and request everytime you need the database a database object. This results in something like this
$db = DB::instance();
where DB::instance is declared something like this
class DB {
//...
private static $instance;
public static function instance() {
if (self::$instance == null) {
self::$instance = new self();
}
}
//...
}
<?php
mysql_select_db('foo',mysql_connect('localhost','root',''))or die(mysql_error());
session_start();
function antiinjection($data)
{
$filter_sql = stripcslashes(strip_tags(htmlspecialchars($data,ENT_QUOTES)));
return $filter_sql;
}
$username = antiinjection($_POST['username']);
$password = antiinjection($_POST['password']);
/* student */
$query = "SELECT * FROM student WHERE username='$username' AND password='$password'";
$result = mysql_query($query)or die(mysql_error());
$row = mysql_fetch_array($result);
$num_row = mysql_num_rows($result);
/* teacher */
$query_teacher = mysql_query("SELECT * FROM teacher WHERE username='$username' AND password='$password'")or die(mysql_error());
$num_row_teacher = mysql_num_rows($query_teacher);
$row_teahcer = mysql_fetch_array($query_teacher);
if( $num_row > 0 ) {
$_SESSION['id']=$row['student_id'];
echo 'true_student';
}else if ($num_row_teacher > 0){
$_SESSION['id']=$row_teahcer['teacher_id'];
echo 'true';
}else{
echo 'false';
}
?>
and in the php file insert javascript
<script>
jQuery(document).ready(function(){
jQuery("#login_form1").submit(function(e){
e.preventDefault();
var formData = jQuery(this).serialize();
$.ajax({
type: "POST",
url: "login.php",
data: formData,
success: function(html){
if(html=='true')
{
window.location = 'folder_a/index.php';
}else if (html == 'true_student'){
window.location = 'folder_b/index.php';
}else
{
{ header: 'Login Failed' };
}
}
});
return false;
});
});
</script>
another connection
<?php
class DbConnector {
var $theQuery;
var $link;
function DbConnector(){
// Get the main settings from the array we just loaded
$host = 'localhost';
$db = 'db_lms1';
$user = 'root';
$pass = '';
// Connect to the database
$this->link = mysql_connect($host, $user, $pass);
mysql_select_db($db);
register_shutdown_function(array(&$this, 'close'));
}
//*** Function: query, Purpose: Execute a database query ***
function query($query) {
$this->theQuery = $query;
return mysql_query($query, $this->link);
}
//*** Function: fetchArray, Purpose: Get array of query results ***
function fetchArray($result) {
return mysql_fetch_array($result);
}
//*** Function: close, Purpose: Close the connection ***
function close() {
mysql_close($this->link);
}
}
?>
I try to test a method that makes a SELECT query and return the rows found. I would like to check that this method doesn't return something else, given a dataset. I found so many docs about creating the dataset but nothing about using it in my case... Thanks for your help.
The method to test is:
class A
{
public static function myMethod()
{
$result = mysql_query("SELECT * FROM user");
[...]
return $rows;
}
}
The test class is:
class ATest extends PHPUnit_Extensions_Database_TestCase
{
protected $pdo;
public function __construct()
{
$this->pdo = new PDO('mysql:host=localhost;dbname=db_name',
'login', 'password');
}
public function getConnection()
{
return $this->createDefaultDBConnection($this->pdo, 'db_name');
}
public function getDataSet()
{
return $this->createFlatXMLDataSet('mydataset.xml');
}
public function testMyMethod()
{
$actual = A::myMethod();
$this->assertEquals(array([...]), $actual);
// For this test, I get a mySQL error "No database selected"
// in A::myMethod()!
}
}
Here is the content of mydataset.xml:
<?xml version="1.0" ?>
<dataset>
<user iduser="1" name="John" />
<user iduser="2" name="James" />
</dataset>
what I did in my case was I made the connection to the database using pdo like so:
static private $pdo=null;
private $conn=null;
public function getConnection()
{
if($this->conn===null)
{
if(self::$pdo===null)
{
self::$pdo = new PDO("mysql:host=yourhost;dbname=yourdbname_",
"yourusername", "yourpassword");
}
$this->conn= $this->createDefaultDBConnection(self::$pdo, 'yourdbname_');
return $this->conn;
}
},
then as for the test, this block below gets all the values in the testdb and compares it with the xml file.
public function testGetAll()
{
$resultingTable = $this->db
->createQueryTable("yourtable",
"SELECT * FROM yourtable");
$expectedTable = $this->getDataSet()
->getTable("yourtable");
$this->assertTablesEqual($expectedTable,
$resultingTable);
}
That worked fine for me and should allow you get all the values from the testdb and assert that they are the same with the xml values.
Just like in your real application, you need to connect to the database before you can call it. The mysql_query() function relies on a previous call having been made to mysql_connect(). If you're only calling the one class method in isolation, then you won't have called the connect function, so you won't have a connection, and so your query command won't know what database it needs to query.
The PDO connection being used in the test class is explicitly separate from and not used by the methods being tested (this applies even if those methods also use PDO); you need to create a connection for the query.
The solution here is to include a call to your DB connection method at the start of the test. This could be in the unit test method, or in the setUp() method of the test class, or in a bootstrap file that PHPUnit calls before running any of the tests. Which of these you use will depend on how many DB tests you need to run and across how many test classes.
Straying slightly off topic, but still relevant: I note that your code is using the old mysql_xxx() functions (ie mysql_query()). It would be advisable to avoid using these functions, as they are obsolete and insecure, and in the process of being deprecated by the PHP dev team. You will therefore find yourself unable to upgrade your PHP version in the future if you keep using them.
Use mysqli_xxx() instead (or PDO, as per your test class).
Back on topic, and in fact doing this will also lead you toward fixing the problem you're having anyway, since both mysqli and PDO require the connection object to be available when calling their functions/methods, so you'll have to have a valid connection object in order to even have valid syntax to call the query. Switching to mysqli or PDO will therefore force you to write your code in a way that solves the problem in the question.
I am currently using PHPUnit and DBUnit for my project. I have a problem in DBUnit because DBUnit PHPUnit_Extensions_Database_TestCaseSrc class does not seem to be truncating the existing data on the test db. So this makes my insertion tests fail after only working for one time.
I am using mysql and here is my code :
abstract class Generic_Tests_DatabaseTestCase extends PHPUnit_Extensions_Database_TestCase
{
// only instantiate pdo once for test clean-up/fixture load
static private $pdo = null;
// only instantiate PHPUnit_Extensions_Database_DB_IDatabaseConnection once per test
private $conn = null;
final public function getConnection()
{
if ($this->conn === null) {
if (self::$pdo == null) {
self::$pdo = new PDO( "mysql:dbname=db;host=localhost", "root", "pass" );
}
$this->conn = $this->createDefaultDBConnection(self::$pdo, "db");
}
return $this->conn;
}
}
class DbopTest extends Generic_Tests_DatabaseTestCase
{
private $db;
protected function setup(){
$this->db = null;
}
public function getDataSet(){
return $this->createMySQLXMLDataSet(dirname(__FILE__) . '/../rows.xml');
}
...
}
So how can I fix this problem? What is it that I do wrong here?
If you override the setUp method, PHPUnit won't automatically call your getDataSet method. You need to take care that you call the parent::setUp method as well, otherwise PHPUnit does not know what to do ;).
I came across this issue myself and this is how I resolved it after a bit of digging into the PHPUnit sourcecode. It looks like the default behavior for the PHPUnit_Extensions_Database_TestCase class is to return PHPUnit_Extensions_Database_Operation_Factory::NONE(). For what you need, and how the PHPUnit document seems to imply how it's supposed to work, you'll want to override the method to return PHPUnit_Extensions_Database_Operation_Factory::TRUNCATE().
Luckily, this is fairly straight-forward. You just need to add the following to your TestCase class.
protected function getTearDownOperation()
{
return \PHPUnit_Extensions_Database_Operation_Factory::TRUNCATE();
}
Before this I was manually truncating tables in my Teardown() method, but I think you'll agree that this solution is much better.
Not expecting many too kudos for this answer, but I have spent several hours trying to figure out why one of my test database tables was not getting truncated, causing the same duplicate entry error described above. My getDataSet() looked like
function getDataSet() {
$files = array('languages','interpreters','interp_languages',
'interp_events','deft_events',
//etc
);
$dataSets = array();
foreach ($files as $file) {
$dataSets[] = new PHPUnit_Extensions_Database_DataSet_MysqlXmlDataSet(
$this->files_dir."/$file.xml");
}
return new PHPUnit_Extensions_Database_DataSet_CompositeDataSet($dataSets);
}
and the technique was working fine on other test classes. It happens that I inadvertentely left out one of my xml data file names from $files, therefore DbUnit was not loading that data file, ergo not truncating the table. But because there were plenty of rows left over in the table from other tests that were using that same data file, it was not obvious (to me) what was happening.
Hope it saves someone else from tearing her/his eyeballs out some day.
You need to have a getDataSet() method otherwise PHPUnit assumes you have no data to fixturize.
http://www.phpunit.de/manual/3.6/en/database.html
The getDataSet() method defines how the initial state of the database should look before each test is executed. The state of a database is abstracted through the concepts DataSet and DataTable both being represented by the interfaces PHPUnit_Extensions_Database_DataSet_IDataSet and PHPUnit_Extensions_Database_DataSet_IDataTable. The next section will describe in detail how these concepts work and what the benefits are for using them in database testing.
For the implementation we only need to know that the getDataSet() method is called once during setUp() to retrieve the fixture data-set and insert it into the database. In the example we are using a factory method createFlatXMLDataSet($filename) that represents a data-set through an XML representation.
I've looked through the various questions on unit testing but can't find one that specifically answers this question.
I've got several PHP classes that contain functions that look like this:
static function _setSuspended($Suspended, $UserID)
{
try {
$con = Propel::getConnection();
$c1 = new Criteria();
$c1->add(DomainsPeer::USERID,$UserID);
$update = new Criteria();
$update->add(DomainsPeer::SUSPENDED,$Suspended);
BasePeer::doUpdate($c1, $update, $con);
return true;
} catch(PropelException $e) {
return $e->getMessage();
}
}
I'm using Propel as my ORM. I've read through various unit testing topics that talk about creating 'Mocks' and 'Stubs' and what not but I have not been able to find anything that specifically tells you how to test a function like above.
My thinking goes something like: I need to test the function above so I would want to call it. But if I call it, it uses Propel as the ORM and according to the Unit Testing principles I should isolate each function by itself.
I just don't see a way to do that. What am I missing here?
I've found that mocking the ORM doesn't give me any confidence because the ORM configuration never gets tested. ORMs also have lots of action at a distance effects which can give false confidence with unit tests. Mocking the database driver or providing an alternate in-memory database gives me much higher confidence my code is correct and is about as hard as mocking the ORM.
SQLite is a great in-memory database for unit testing. It's on the PDO supported database list. (PDO is the Propel 1.3 database driver.) If you don't want to use an in-memory database, you might be able to find a PDO mock already written.
This is a generic answer in that I'm not familiar with Propel at all and only somewhat more familiar with PHP. The basic answer is that you use dependency injection. Instead of referring directly to your ORM, you create a wrapper around it, then inject the wrapper into your class/function to actually use. To do unit testing, then you create a mock or fake version of the wrapper that doesn't interface to the ORM but instead lets you configure the responses from the wrapper to your method invocations. This allows you to factor out the ORM when unit testing your functions.
I was trying to tackle the same problem while building a PHPUnit plugin for Symfony. I ended up approaching it similarly to Django's test framework — use a separate database/connection, and destroy and rebuild it before every test.
I found that I was also able to get away with only rebuilding the test database before the first test in a test run (or if a test explicitly instructs it to); before the other tests, it just deletes all data to speed things up a little.
I've been reading Misko Hevery's blog about testing a lot lately. It covers this situation; you'd need to use DI (dependency injection).
I am struggling myself with this a bit as well, and I also use propel.
For one, you could move the "suspend" method to the "Object" class rather than the peer. For this particular function anyway, you don't need to use the static methods to achieve this. Your API could look like:
MyObjectPeer::retrieveByPK(1)->suspend();
This would be testable via normal unit testing methods.
If it's really the database that needs to be tested, then AFAIK you need to actually have the DB involved in the test. I am using ltree and postgis a lot in my current project and I can't think of any other way to run unit tests for the model logic that depends on the DB other than to include it in my tests.
This is an exemple of a class with hard dependency which can't be unit testable.
We could be able to test with a connection to another database but then, it's not a Unit Test anymore but an Integration Test.
The better alternative that I think about is to have an QueryFactory class that will wrap all the different methods that you need and then, you will be able to mock it.
First in first I create an interface
interface iQueryFactory
{
function firstFunction($argument);
function secondFunction($argument, $argument2);
}
The QueryFactory with all your ORM request we need
class QueryFactory implements iQueryFactory
{
function firstFunction($argument)
{
// ORM thing
}
function secondFunction($argument, $argument2)
{
// ORM stuff
}
}
There is the business logique with the injection of the query factory
class BusinessLogic
{
protected $queryFactory;
function __construct($queryFactoryInjection)
{
$this->queryFactory= $queryFactoryInjection;
}
function yourFunctionInYourBusinessLogique($argument, $argument2)
{
// business logique
try {
$this->queryFactory->secondFunction($argument, $argument2);
} catch (\Exception $e) {
// log
// return thing
}
// return stuff
}
}
The mock part, note that I don't use a mock framework for my exemple (btw you can create a response setter)
class QueryFactoryMock implements iQueryFactory
{
function firstFunction($argument)
{
if (is_null($argument))
{
throw new \Exception("");
}
else
{
return "succes";
}
}
function firstFunction($argument, $argument2)
{
// sutff
}
}
Then finally the Unit Tests who test our business logic with the mock implementation
class BusinessLogicTest extends PHPUnit_Framework_TestCase
{
public function setUp()
{
require_once "BusinessLogic.php";
}
public function testFirstFunction_WhenInsertGoodName()
{
$queryMockup = new QueryFactoryMock();
$businessLogicObject = new BusinessLogic($queryMockup);
$response = $businessLogicObject ->firstFunction("fabien");
$this->assertEquals($response, "succes");
}
public function testFirstFunction_WhenInsetNull()
{
$queryMockup = new QueryFactoryMock();
$businessLogicObject = new BusinessLogic($queryMockup);
$response = $businessLogicObject->firstFunction(null);
$this->assertEquals($response, "fail");
}
}