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Simulating other operating systems

MockFileSystem can pretend to be a different operating system than the host it runs on. Pass a SimulationMode in the constructor:

var linuxFileSystem = new MockFileSystem(o =>
    o.SimulatingOperatingSystem(SimulationMode.Linux));
// case-sensitive, '/' separator, single root

var windowsFileSystem = new MockFileSystem(o =>
    o.SimulatingOperatingSystem(SimulationMode.Windows));
// case-insensitive, '\\' separator, drive letters

var macFileSystem = new MockFileSystem(o =>
    o.SimulatingOperatingSystem(SimulationMode.MacOS));

Because the entire test suite runs against the real file system on Linux, macOS and Windows and against each SimulationMode in CI, the simulated behaviour stays in lock-step with the genuine platform behaviour over time.

Why simulate​

  • Catch case-sensitivity bugs that only show up on Linux from a Windows dev machine.
  • Verify path-handling code on Windows from a Linux CI runner.
  • Test drive-letter handling without spinning up a Windows job.

If you only need the host's own behaviour, omit SimulatingOperatingSystem - MockFileSystem defaults to whichever OS it is running on.

SimulatingOperatingSystem is only available when running on .NET 6 or newer. On earlier targets, the mock always uses the host OS.