dependency injection

dependencyinjection.php

// DB Interface
interface DBInterface {
  public function query( $myQuery );
}

// Database Dependency Class
class Database implements DBInterface
{
  public function query( $myQuery ) {
    return $myQuery;
  }
}

// Class using Database class
class someOtherClass {

  private $_db;

  public function __construct( DBInterface $db ) {
    $this->_db = $db;
  }
  
  public function executeQuery( $myQuery ) {
  
    // blah blah
    $query = $this->_db->query( $myQuery );
    
    return 'executeQuery - ' .$query;
  }
}


// Unit Test

class mockDatabase implements DBInterface {
  public function query( $myQuery ) {
    return 'mockQuery';
  }
}

class test_someOtherClass {

  private $_someOtherClass;

  public function __construct() {
    
    $mockDB = new mockDatabase();
    $this->_someOtherClass = new someOtherClass( $mockDB );
  }

  public function test_executeQuery() {
    
    $retVal = $this->_someOtherClass->executeQuery('test');

    return ( $retVal === 'executeQuery - mockQuery' ) ? 'test passed' : 'test failed';
  }
}