420 - Test coverage: GetAvailablePaymentMethodsTest for Guest

1. Add Magento/Payment/_files/disable_all_active_payment_methods.php

dev/tests/api-functional/testsuite/Magento/GraphQl/Quote/Guest/GetAvailablePaymentMethodsTest.php

@@ -86,7 +86,7 @@ public function testGetPaymentMethodsFromAnotherCustomerCart()
 
     /**
      * @magentoApiDataFixture Magento/Checkout/_files/quote_with_simple_product_saved.php
-     * @magentoApiDataFixture Magento/Payment/_files/disable_all_payment_methods.php
+     * @magentoApiDataFixture Magento/Payment/_files/disable_all_active_payment_methods.php
      */
     public function testGetPaymentMethodsIfPaymentsAreNotSet()
     {

dev/tests/integration/testsuite/Magento/Payment/_files/disable_all_active_payment_methods.php

@@ -0,0 +1,37 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+use Magento\Config\Model\Config;
+use Magento\Framework\App\Config\ScopeConfigInterface;
+use Magento\TestFramework\Helper\Bootstrap;
+
+$processConfigData = function (Config $config, array $data) {
+    foreach ($data as $key => $value) {
+        $config->setDataByPath($key, $value);
+        $config->save();
+    }
+};
+
+$objectManager          = Bootstrap::getObjectManager();
+$paymentMethodList      = $objectManager->get(\Magento\Payment\Api\PaymentMethodListInterface::class);
+$rollbackConfigKey      = 'test/payment/disabled_payment_methods';
+$configData             = [];
+$disabledPaymentMethods = [];
+
+// Get all active Payment Methods
+foreach ($paymentMethodList->getActiveList(\Magento\Store\Model\Store::DEFAULT_STORE_ID) as $paymentMethod) {
+    $configData['payment/' . $paymentMethod->getCode() . '/active'] = 0;
+    $disabledPaymentMethods[] = $paymentMethod->getCode();
+}
+// Remember all manually disabled Payment Methods for rollback
+$configData[$rollbackConfigKey] = implode(',', $disabledPaymentMethods);
+
+/** @var Config $defConfig */
+$defConfig = $objectManager->create(Config::class);
+$defConfig->setScope(ScopeConfigInterface::SCOPE_TYPE_DEFAULT);
+
+$processConfigData($defConfig, $configData);

dev/tests/integration/testsuite/Magento/Payment/_files/disable_all_active_payment_methods_rollback.php

@@ -0,0 +1,33 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+use Magento\Framework\App\Config\ScopeConfigInterface;
+use Magento\Framework\App\Config\Storage\WriterInterface;
+use Magento\TestFramework\Helper\Bootstrap;
+
+$objectManager     = Bootstrap::getObjectManager();
+$rollbackConfigKey = 'test/payment/disabled_payment_methods';
+
+$configWriter        = $objectManager->create(WriterInterface::class);
+$rollbackConfigValue = $objectManager->get(\Magento\Store\Model\StoreManagerInterface::class)
+    ->getStore(\Magento\Store\Model\Store::DEFAULT_STORE_ID)
+    ->getConfig($rollbackConfigKey);
+
+$disabledPaymentMethods = [];
+if (!empty($rollbackConfigValue)) {
+    $disabledPaymentMethods = explode(',', $rollbackConfigValue);
+}
+
+if (count($disabledPaymentMethods)) {
+    foreach ($disabledPaymentMethods as $keyToRemove) {
+        $configWriter->delete(sprintf('payment/%s/active', $keyToRemove));
+    }
+}
+$configWriter->delete($rollbackConfigKey);
+
+$scopeConfig = $objectManager->get(ScopeConfigInterface::class);
+$scopeConfig->clean();