FooConfiguration example

$container->prependExtensionConfig('foo', []);

        $pass = new MergeExtensionConfigurationPass();
        $pass->process($container);
    }

    public function testExtensionConfigurationIsTrackedByDefault()
    {
        $extension = $this->getMockBuilder(FooExtension::class)->onlyMethods(['getConfiguration'])->getMock();
        $extension->expects($this->exactly(2))
            ->method('getConfiguration')
            ->willReturn(new FooConfiguration());

        $container = new ContainerBuilder(new ParameterBag());
        $container->registerExtension($extension);
        $container->prependExtensionConfig('foo', ['bar' => true]);

        $pass = new MergeExtensionConfigurationPass();
        $pass->process($container);

        $this->assertContainsEquals(new FileResource(__FILE__), $container->getResources());
    }