September 2025 Testing Guidance

This month’s Microsoft Patch Tuesday updates require focused testing across network infrastructure, graphics subsystems, and authentication components. September 2025 brings significant updates to core networking protocols, DirectX graphics functionality, and Bluetooth connectivity that demand immediate validation. These updates affect both client and server environments, with particular attention needed for organizations using Routing and Remote Access Services (RRAS) and those with complex Bluetooth device management requirements.

Network Infrastructure & Connectivity

Microsoft has updated core network communication components including socket handling and IPv6 functionality. These low-level network changes can significantly impact enterprise connectivity and require comprehensive validation across different network scenarios:

• Send and receive packets over the network using both IPv4 and IPv6 protocols
• Test large file transfers over IPv6 networks to validate performance and stability
• Validate various network traffic conditions including file transmission, remote desktop connections, and web browsing
• Open web browsers and connect to multiple sites repeatedly to test connection stability and download files from various websites to ensure download functionality remains intact
• Test messaging applications like Microsoft Teams or Skype with connect/disconnect/reconnect cycles

Graphics, DirectX & Application Guard

This month includes substantial updates to graphics subsystems and security isolation components which will require a test cycle to ensure that graphics applications render correctly without screen corruption or performance degradation:

• DirectX functionality and Windows Defender Application Guard receive critical updates that require validation:
• Execute applications and UWP apps that use DirectComposition functionality, ensuring no flickering or display anomalies occur
• Test games that utilize DirectX APIs to confirm proper graphics rendering
• Test DirectX API usage on Hyper-V guests with GPU-PV enabled across multi-threaded scenarios
• Validate Windows Defender Application Guard functionality with Office applications and Microsoft Edge

Authentication & Directory Services

Critical updates to authentication components require thorough testing of domain and workstation authentication scenarios:

• Test regular authentication and authorization scenarios in domain environments
• Use NTLM and Kerberos protocols to authenticate users on both workstation-joined and domain-joined machines
• Exercise the LogonUserEx API from client applications to ensure programmatic authentication works correctly
• Test secondary logon (RunAs) scenarios across different user contexts
• Validate CredSSP (Credential Security Support Provider) functionality
• Test Active Directory components including Active Directory Certificate Services and LDAP operations

Bluetooth Device Management

This month’s updates to Bluetooth require device pairing and management testing that includes:

• Simultaneous Device Management: Pair and unpair multiple Bluetooth devices (earbuds, keyboards, speakers) simultaneously via SwiftPair or Settings to stress-test concurrent operations
• Multiple Adapter Support: Connect both internal and external Bluetooth adapters and test device pairing using each adapter independently
• PIN and Consent Flow: Use Bluetooth keyboards requiring PIN entry, test pairing with correct and incorrect PINs, and verify graceful error handling and retry mechanisms
• Monitor for UI hangs, pairing failures, or stale device entries during intensive Bluetooth operations

Routing and Remote Access Services (RRAS)

Significant updates to RRAS components require comprehensive testing for organizations using routing and remote access functionality:

• Perform configuration and viewing operations using the Routing and Remote Access management console for both local and remote installations
• Test different property pages (DHCP, NAT, RIP, IGMP, BOOTP) to ensure they display correct information for valid configurations
• Validate that invalid configurations are handled correctly by showing appropriate error dialogs or preventing access to misconfigured sections
• Exercise remote RRAS server management to ensure remote administration capabilities remain functional

HTTP Services & Web Infrastructure

Updates to core HTTP handling components require validation of modern web protocols and caching mechanisms:

• Enable Branch Cache and configure HTTP server applications to cache responses
• Send HTTP/2 and HTTP/3 requests to validate next-generation protocol support
• Ensure request-response cycles complete without system crashes or bug-checks
• Test web service functionality across different HTTP protocol versions

Filesystem & Storage Operations

Core filesystem components received patches and updates affecting file operations and virtual disk management will require the following tests:

• Use PowerShell’s Mount-DiskImage cmdlet to attach VHD files to NTFS volumes
• Perform comprehensive file operations on mounted volumes including read, write, and delete operations
• Test App Silos functionality with applications that perform filesystem access

Additional Application Testing

• Privacy and capability management components require testing to ensure user privacy controls function correctly. Validate that privacy permission changes take effect immediately and persist across system reboot.
• Validate VPN connection scenarios across different VPN providers and protocols
• Test applications using XAML UI frameworks including Microsoft Photos and modern UWP applications
• Verify Remote PowerShell functionality using Invoke-Command and New-PSSession cmdlets

This month’s updates emphasize network reliability, graphics performance, and security isolation. Organizations should prioritize testing in network-intensive environments and those with complex authentication requirements. Pay particular attention to Bluetooth device management if your environment relies heavily on wireless peripherals, and ensure RRAS functionality is thoroughly validated before deploying to production routing infrastructure.