Isolate unit tests in Symfony2 http://php-and-symfony.matthiasnoback.nl/2011/10/symfony2-use-a-bootstrap-file-for-your-phpunit-tests-and-run-some-console-commands/ and then use this as your bootstrap to load migrations & fixtures.

bootstrap.php

<?php

require_once __DIR__ . '/bootstrap.php.cache';
require_once __DIR__ . '/AppKernel.php';
 
use Symfony\Bundle\FrameworkBundle\Console\Application;
use Symfony\Component\Console\Output\ConsoleOutput;
use Symfony\Component\Console\Input\ArrayInput;
 
use Doctrine\Bundle\DoctrineBundle\Command\DropDatabaseDoctrineCommand;
use Doctrine\Bundle\DoctrineBundle\Command\CreateDatabaseDoctrineCommand;
use Doctrine\Bundle\MigrationsBundle\Command\MigrationsMigrateDoctrineCommand;
use Doctrine\Bundle\FixturesBundle\Command\LoadDataFixturesDoctrineCommand;
 
$kernel = new AppKernel('test', true); // create a "test" kernel
$kernel->boot();
 
$application = new Application($kernel);
 
// add the database:drop command to the application and run it
$command = new DropDatabaseDoctrineCommand();
$application->add($command);
$input = new ArrayInput(array(
    'command' => 'doctrine:database:drop',
    '--force' => true,
));
$command->run($input, new ConsoleOutput());
 
// This stops a bug where Drop Database does not close the handle properly & causes subsequent
// "database not found" errors.
$connection = $application->getKernel()->getContainer()->get('doctrine')->getConnection();
if ($connection->isConnected()) {
    $connection->close();
}

// add the database:create command to the application and run it
$command = new CreateDatabaseDoctrineCommand();
$application->add($command);
$input = new ArrayInput(array(
    'command' => 'doctrine:database:create',
));
$command->run($input, new ConsoleOutput());

// Run the database migrations, with --quiet because they are quite
// chatty on the console.
$command = new MigrationsMigrateDoctrineCommand();
$application->add($command);
$input = new ArrayInput(array(
    'command' => 'doctrine:migrations:migrate',
    '--quiet' => true,
    '--no-interaction' => true,
));
$input->setInteractive(false);
$command->run($input, new ConsoleOutput(ConsoleOutput::VERBOSITY_QUIET));

// and load the fixtures
$command = new LoadDataFixturesDoctrineCommand();
$application->add($command);
$input = new ArrayInput(array(
    'command' => 'doctrine:fixtures:load',
    '--quiet',
));
$input->setInteractive(false);
$command->run($input, new ConsoleOutput());

Since you always recreate database you might as well use sqLite in memory. In this case all you need is this command before loading fixtures:

 . . .

$application = new Application($kernel);

$command = new UpdateSchemaDoctrineCommand();
$application->add($command);
$input = new ArrayInput(array(
    '--force' => true
));

$command->run($input, new ConsoleOutput());

That makes bootstrapping faster as well.