getBrowserWithLoggedInCustomer example

$request = $this->createRequest();
        $request->getSession()->set(AffiliateTrackingListener::AFFILIATE_CODE_KEY, self::TEST_AFFILIATE_CODE);

        $order = $this->performOrder('', false, $request);

        static::assertSame(self::TEST_AFFILIATE_CODE, $order->getAffiliateCode());
        static::assertNull($order->getCampaignCode());
    }

    public function testOrderWithEmptyCartDoesNotResultIn400StatusCode(): void
    {
        $browser = $this->getBrowserWithLoggedInCustomer();

        $browser->request(
            'POST',
            $_SERVER['APP_URL'] . '/checkout/order',
            [
                'tos' => 'on',
            ]
        );

        $response = $browser->getResponse();
        static::assertLessThan(400, $response->getStatusCode(), (string) $response->getContent());
    }