Testing

​

Overview

​

Testing Environments

​

Recommended Test Setup

1. Virtual Machine (Safest)
   • VMware Workstation, VirtualBox, or Hyper-V
   • Easy to snapshot and revert
   • Isolated from host system
   • Supports nested virtualization for testing
2. Dedicated Test Machine
   • Secondary computer for driver testing
   • Can recover via Safe Mode if needed
   • Real hardware testing environment
3. Dual Boot Configuration
   • Separate Windows installation for testing
   • Production OS remains safe
   • Requires disk partitioning

​

Environment Checklist

• System snapshot or backup created
• Test signing mode enabled (for development builds)
• WinDbg or kernel debugger configured (optional but recommended)
• All personal data backed up
• Safe Mode boot option verified
• Recovery USB or installation media available

​

Pre-Installation Testing

​

Static Analysis

<RunCodeAnalysis>true</RunCodeAnalysis>
<EnablePREfast>true</EnablePREfast>

• Memory leaks
• Buffer overflows
• Uninitialized variables
• Invalid pointer usage
• NTSTATUS handling errors

​

Driver Verifier (Static Check)

# Check for basic issues
verifier /query

# Analyze driver binary (static)
verifier /flags 0x209BB /driver MttVDD.dll

• 0x209BB - Standard settings
• 0xFFFFFFFF - All tests (very strict)

​

Signature Verification

# Verify signature
signtool verify /v /pa MttVDD.cat
signtool verify /v /pa MttVDD.dll

​

Installing Test Drivers

​

Enable Test Signing

# Run as Administrator
bcdedit /set testsigning on
# Reboot required

• “Test Mode” watermark appears on desktop
• Check Settings → System → About → Windows specifications

​

Manual Driver Installation

1. Open Device Manager (devmgmt.msc)
2. Click Action → Add legacy hardware
3. Select Install the hardware that I manually select
4. Choose Display adapters
5. Click Have Disk
6. Browse to MttVDD.inf
7. Follow installation wizard

# Run as Administrator
cd path\to\driver\output

# Install driver package
pnputil /add-driver MttVDD.inf /install

# Verify installation
pnputil /enum-drivers | findstr "MttVDD"

​

Verifying Installation

# Check driver status
sc query MttVDD

# List loaded drivers
driverquery | findstr "MttVDD"

# Check Device Manager
# Look under "Display adapters" for "Virtual Display Driver"

# Open Event Viewer
eventvwr.msc

# Navigate to:
# Windows Logs → System
# Filter for source: "MttVDD" or "DriverFrameworks-UserMode"

​

Runtime Testing

​

Basic Functionality Tests

​

1. Monitor Creation

# Check display configuration
displayswitch /internal
displayswitch /external

# PowerShell: List all displays
Get-CimInstance -Namespace root\wmi -ClassName WmiMonitorBasicDisplayParams

• Virtual monitors appear in Display Settings
• Correct number of monitors (based on vdd_settings.xml)
• Monitors show as “Active” in Device Manager

​

2. Resolution Configuration

1. Open Settings → System → Display
2. Select virtual monitor
3. Try different resolutions from dropdown
4. Apply and verify no crashes

# Change resolution (requires third-party tool or API call)
# Example: Set to 1920x1080

​

3. Refresh Rate Testing

1. Display Settings → Advanced display
2. Select virtual monitor
3. Check available refresh rates
4. Change to different rate (e.g., 60Hz → 144Hz)
5. Verify smooth operation

​

4. HDR Capability

1. Display Settings → HDR
2. Enable HDR for virtual monitor
3. Verify no errors
4. Test HDR content playback

​

5. Multi-Monitor Configuration

1. Create 2+ virtual monitors
2. Arrange displays in Settings
3. Extend desktop across monitors
4. Move windows between displays
5. Test taskbar on each monitor

​

Application Compatibility Tests

​

Streaming Applications

• OBS Studio
• Parsec
• Moonlight
• Steam Remote Play
• Virtual Desktop (VR)

• Application detects virtual monitor
• Can select virtual monitor as source
• Streaming works without artifacts
• Performance is acceptable

​

VR Applications

• Oculus/Meta Quest Link
• SteamVR
• Virtual Desktop

• VR app can use virtual monitor
• No performance degradation
• Display synchronization works

​

Recording Software

• OBS Studio
• NVIDIA ShadowPlay (if applicable)
• Windows Game Bar

• Can record from virtual display
• No frame drops
• Audio/video sync maintained

​

Stress Testing

​

1. Rapid Configuration Changes

# Script: Change resolution rapidly
for ($i=0; $i -lt 100; $i++) {
    # Toggle between resolutions
    # Monitor for crashes
}

​

2. Multiple Monitor Cycling

• Install driver → uninstall → reinstall
• Create monitors → delete → recreate
• Monitor system stability

​

3. Long-Duration Testing

• 24+ hours continuous operation
• Monitor for memory leaks
• Check Event Viewer for errors
• Verify performance doesn’t degrade

​

4. GPU Stress Testing

• Run 3DMark or FurMark on physical display
• Simultaneously stream from virtual display
• Monitor temperatures and stability

​

GPU Adapter Testing

<Adapter>
  <TargetGPU>NVIDIA GeForce RTX 3080,1</TargetGPU>
</Adapter>

1. Driver uses specified GPU
2. Falls back to best GPU if name incorrect
3. PCI bus number selection works
4. Multi-GPU systems handled correctly

​

EDID Profile Testing

1. Place EDID file in EDID directory
2. Reference in vdd_settings.xml
3. Restart driver or recreate monitor
4. Verify:
   • Monitor name matches EDID
   • Supported resolutions match EDID
   • Color spaces and capabilities correct

​

Debugging Techniques

​

WPP Tracing

# Start tracing session
tracelog -start MyTrace -guid MttVDD.guid -f MyTrace.etl -flags 0xFFFF

# Reproduce issue

# Stop tracing
tracelog -stop MyTrace

# Convert to readable format
tracefmt MyTrace.etl -o MyTrace.txt

type MyTrace.txt | more

​

Kernel Debugging

1. Install WinDbg (from Windows SDK)
2. Configure kernel debugging:
   bcdedit /debug on
   bcdedit /dbgsettings serial debugport:1 baudrate:115200
   
3. Connect debugger from another machine or VM
4. Set breakpoints in driver code

!analyze -v          # Analyze crash dump
lm                    # List loaded modules
k                     # Stack trace
dt                    # Display type
!process 0 0          # List processes

​

Event Viewer Analysis

1. Open Event Viewer (eventvwr.msc)
2. Navigate to Windows Logs → System
3. Filter current log:
   • Event sources: “DriverFrameworks-UserMode”, “MttVDD”
   • Event level: Warning, Error, Critical

• Event ID 10016 - DCOM permission issues (usually benign)
• Event ID 219 - Driver failed to start
• Event ID 7000 - Service control manager errors

​

Memory Leak Detection

# Check driver memory over time
while ($true) {
    Get-Process -Name "WUDFHost" | Select-Object WorkingSet64, PrivateMemorySize64
    Start-Sleep -Seconds 60
}

# Enable verifier on MttVDD
verifier /flags 0x209BB /driver MttVDD.dll

# Reboot and test

# Disable verifier when done
verifier /reset

​

Common Issues and Diagnostics

​

Driver Fails to Load

1. Check Event Viewer for specific error codes
2. Verify driver signature: signtool verify /v /pa MttVDD.dll
3. Ensure test signing enabled if using test certificate
4. Check Device Manager device status (right-click → Properties)

• Solution: Enable test signing, install certificate to Trusted Root

• Solution: Reinstall driver, verify file integrity

​

Blue Screen / System Crash

1. Note STOP code (e.g., DRIVER_IRQL_NOT_LESS_OR_EQUAL)
2. Check minidump files in C:\Windows\Minidump\
3. Analyze with WinDbg: !analyze -v
4. Look for driver name in stack trace

• Invalid pointer dereference
• Memory access at wrong IRQL level
• Buffer overrun
• Resource leak

1. Boot into Safe Mode (F8 during boot)
2. Uninstall driver via Device Manager
3. Disable test signing if needed
4. Fix code issues and rebuild

​

Performance Issues

1. Monitor GPU usage (Task Manager → Performance)
2. Check CPU usage by WUDFHost process
3. Profile with Windows Performance Recorder (WPR)
4. Review SwapChain processing logic

• Inefficient frame processing
• Not releasing buffers promptly
• Excessive logging/tracing
• GPU/CPU mismatch

​

Display Artifacts

1. Verify GPU adapter selection
2. Check EDID configuration
3. Test different resolutions/refresh rates
4. Review Direct3D device initialization

​

Configuration Not Applied

1. Verify XML file at C:\VirtualDisplayDriver\vdd_settings.xml
2. Check XML syntax (use XML validator)
3. Review Event Viewer for parsing errors
4. Add WPP traces to configuration loading code

​

Safe Recovery Procedures

​

Safe Mode Boot

1. Force Safe Mode:
   • Restart computer
   • Press F8 repeatedly during boot
   • Select “Safe Mode”
2. Windows 10/11 Safe Mode:
   • Shift + Restart
   • Troubleshoot → Advanced → Startup Settings → Restart
   • Press 4 or F4 for Safe Mode
3. Uninstall driver in Safe Mode:
   pnputil /delete-driver MttVDD.inf /uninstall
   

​

System Restore

1. Boot from Windows installation media
2. Select “Repair your computer”
3. Troubleshoot → Advanced Options → System Restore
4. Choose restore point before driver installation

​

Last Known Good Configuration

1. Press F8 during boot
2. Select “Last Known Good Configuration”
3. Windows loads previous working driver set

​

Testing Checklist

​

Pre-Installation

• PREfast analysis passes (0 errors)
• Driver signed with valid certificate
• Signature verified with signtool
• Build configuration correct (Release for distribution)

​

Basic Functionality

• Driver installs without errors
• Virtual monitors appear in Display Settings
• All configured monitors created
• Resolutions can be changed
• Refresh rates configurable
• Monitors can be enabled/disabled

​

Advanced Features

• HDR toggle works (if applicable)
• Custom EDID profiles load correctly
• GPU adapter selection functions
• Multi-monitor configuration stable
• vdd_settings.xml changes applied

​

Application Compatibility

• OBS Studio detects virtual monitor
• Streaming applications work
• VR applications compatible (if applicable)
• Recording software functions
• Games/applications render correctly

​

Stability

• No crashes during 24-hour test
• No memory leaks detected
• Event Viewer shows no critical errors
• Rapid configuration changes stable
• System remains responsive

​

Platform Testing

• Tested on x64 Windows 10
• Tested on x64 Windows 11
• Tested on ARM64 (if applicable)
• Multiple GPU configurations tested

​

Next Steps

​

Additional Resources

• Driver Verifier
• WinDbg Documentation
• WPP Software Tracing
• Debugging UMDF Drivers