assertEquals("processed_site1", result);

        // Headers persist in same request, so subsequent headers are additive
        // Test with case insensitive matching
        request.addHeader("X-Forwarded-Host", "TEST.COM");
        result = virtualHostHelper.processVirtualHost(s -> "processed_" + s, "default");
        assertEquals("processed_site1", result); // Still site1 due to header precedence