DF - Fuzz sub-opens test (Reliability)

During a Relative Open Test, (also known as a Sub-open Test) the Fuzz test attempts to open objects in the device's namespace.

During this test, the Fuzz test performs a rapid series of calls to open objects in the namespace of the devices opened by using Basic Open Operations and other open operations. In these calls, the Fuzz test passes a path that begins with the device and includes arbitrary names and nonsense strings of varying length and content.

This test determines how the driver or file system manages open requests in its namespace. In particular, if the driver does not support open requests in its namespace, it must prevent unauthorized access, either by failing the requests, or by setting the FILE_DEVICE_SECURE_OPEN device characteristic when it uses IoCreateDevice or IoCreateDeviceSecure to create the device object.

For more information about the namespace of a device, see Controlling Device Namespace Access.

Test binary: Devfund_FuzzTest.dll Test method: DoSubOpensTest

Test details

  • Device.DevFund.Reliability.BasicReliabilityAndPerformance
  • Device.DevFund.Reliability.BasicSecurity
  • Device.DevFund.DriverFramework.KMDF.Reliability
  • Device.DevFund.DriverFramework.UMDF.Reliability
  • Windows 10, client editions (x86)
  • Windows 10, client editions (x64)
  • Windows Server 2016 (x64)
  • Windows 10, client editions (ARM64)
  • Windows 10, mobile edition (ARM)
  • Windows 10, mobile edition (ARM64)
Supported Releases
  • Windows 10
  • Windows 10, version 1511
  • Windows 10, version 1607
  • Windows 10, version 1703
  • Windows 10, version 1709
  • Windows 10, version 1803
  • Windows 10, version 1809
  • Next update to Windows 10
Expected run time (in minutes) 15
Category Scenario
Timeout (in minutes) 180
Requires reboot false
Requires special configuration true
Type automatic


Additional documentation

Tests in this feature area might have additional documentation, including prerequisites, setup, and troubleshooting information, that can be found in the following topic(s):

Running the test

Before you run the test, complete the test setup as described in the test requirements: Device.Fundamentals Reliability Testing Prerequisites.


For generic troubleshooting of HLK test failures, see Troubleshooting Windows HLK Test Failures.

For troubleshooting information specific to the Device Fundamentals tests in the HLK and WDK, see Device.DevFund additional documentation.

More information


Parameter name Parameter description
DQ A WDTF SDEL query that is used to identify the target device(s) - http://go.microsoft.com/fwlink/?LinkId=232678
Wpa2PskAesSsid Required ONLY if DUT or one of its child devices is a WiFi adapter. Please provide SSID of a WPA2 AES WiFi network that the test can use to test the WiFi adapter. The default is 'kitstestssid'.
Wpa2PskPassword Required ONLY if DUT or one of its child devices is a WiFi adapter. Please provide password of the WPA2 AES WiFi network specified using the Wpa2PskAesSsid parameter. The default is 'password'.
ChangeBufferProtectionFlags True or False. Changes the memory protection flags of buffers passed to the tested device. The memory protection flags alternates between no access, read-only, and read-only with page guard.
Impersonate True or False. Runs the test as a non administrative user.
FillZeroPageWithNull True or False. Maps the zero page and fills it with NULL values. This test identifies drivers that do not verify a pointer reference before dereferencing a pointer.
DoPoolCheck True or False. Monitors the driver's use of the paged and nonpaged system memory pools by using pool tags and lookaside lists. This option also monitors changes in the number of exceptions handled which might indicate errors in exception handling.
DoSync True or False. Also opens device handles in SYNC mode (FILE_SYNCHRONOUS_IO_ALERT). Random read and write operations are skipped.
TestCycles Number of test cycles.
DriverVerifierAdditionalDrivers Additional drivers that should have Driver Verifier enabled
DriverVerifierExcludedFlags Placeholder for Driver Verifier flags that may be manually excluded for the test run
WDKDeviceID Device id of device under test
QueryHardwareID Hardware id of device under test
WDTFREMOTESYSTEM Required ONLY if DUT or one of its child devices is a wired NIC that doesn't have an IPv6 gateway address. If determined to be required, please provide an IPv6 address that the test NIC can ping to test network I/O. Eg: fe80::78b6:810:9c12:46cd
DriverVerifierCustomizeConfiguration Specifies that this test may want to automatically update Driver Verifier settings