In the reported reproduction project [OneTimeSetUp]and [OneTimeTearDown]is used to setup and remove devices. InputTestFixture do not support this and is instead tightly coupled to [SetUp]and [TearDown]hooks of NUnit. The only change needed to the repro project to avoid a crash like this is to replace [OneTimeSetUp]with [SetUp]and [OneTimeTearDown]with [TearDown]. The reason behind this is that InputTestFixture will push a test state as part of Setup() and pop that state as part of TearDown(). This means that only code in-between SetUp and TearDown will be operating on the test instance of the system. If a device is created before SetUp, like in the provided project, it will no longer be a valid instance after SetUp has executed and may contain unsafe pointers into memory that is not valid until the current test ends. Hope this helps.

In addition to the above we have as part of investigating this ticket improved the documentation of InputTestFixture and added checks that throws exceptions if used in an unsupported way to provide better guidance when using it outside what it may support. If desirable to keep devices between multiple tests it is instead recommended to create a custom test fixture for that purpose if the features supported by InputTestFixture are considered insufficient.