FooExtension example

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

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

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

    public function testOverriddenEnvsAreMerged()
    {
        $container = new ContainerBuilder();
        $container->registerExtension(new FooExtension());
        $container->prependExtensionConfig('foo', ['bar' => '%env(FOO)%']);
        $container->prependExtensionConfig('foo', ['bar' => '%env(BAR)%', 'baz' => '%env(BAZ)%']);

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

        $this->assertSame(['BAZ', 'FOO'], array_keys($container->getParameterBag()->getEnvPlaceholders()));
        $this->assertSame(['BAZ' => 1, 'FOO' => 0], $container->getEnvCounters());
    }

    public function testProcessedEnvsAreIncompatibleWithResolve()
    {