Magento2 integration tests magentoConfigFixture getting empty value for obscure field

i am writing integration tests for my custom module that has a configuration field type obscure.
in test file app/code/Foo/Bar/Test/Integration/Model/ConfigTest.php i have code:

<?php

namespace FooBarTestIntegrationModel;

use FooBarModelConfig;
use MagentoFrameworkObjectManagerInterface;
use MagentoTestFrameworkHelperBootstrap;
use PHPUnitFrameworkTestCase;

class ConfigTest extends TestCase
{
    private ?ObjectManagerInterface $objectManager;
    private ?Config $config;

    protected function setUp(): void
    {
        parent::setUp();
        $this->objectManager = Bootstrap::getObjectManager();
        $this->config = $this->objectManager->get(Config::class);
    }

    /**
     * @test
     * @magentoConfigFixture default_website foo_module/bar_api_config/site_key 1x0000000000AA
     */
    public function get_site_key()
    {
        $this->assertEquals('1x0000000000AA', $this->config->getSiteKey());
    }
}

And in app/code/Foo/Bar/Model/Config.php file i have method:

public function getSiteKey(): ?string
    {
        return $this->config->getValue('foo_module/bar_api_config/site_key', ScopeInterface::SCOPE_WEBSITE);
    }

And at app/code/Foo/Bar/etc/adminhtml/system.xml:

<?xml version="1.0"?>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <section id="foo_module" translate="label" type="text" sortOrder="700" showInDefault="1"
                 showInWebsite="1" showInStore="1">
            <resource>Foo_Bar::config</resource>
            <group id="bar_api_config" translate="label" type="text" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
                <field id="site_key" translate="label" type="obscure" sortOrder="10" showInDefault="1" showInWebsite="1" showInStore="0">
                    <label>Sitekey</label>
                    <validate>required-entry</validate>
                    <backend_model>MagentoConfigModelConfigBackendEncrypted</backend_model>
                </field>
            </group>
        </section>
    </system>
</config>

When testcase execute it always return empty "" no matter whatever scope i set. I am missing something here or Magento just don’t have ability to setup obscure field fixture out of the box?