Microsoft provides a free Windows 10 virtual machine for testing. Package maintainers working on Linux and MacOS can use it to test their packages on Windows. See instructions on how to set up the machine automatically for checking R packages.
The set up provides SSH access with bash, so that users can perform most of the tasks from their preferred terminal emulator. Command line tools needed to build R and many R packages from source are pre-installed. Additional tools are available via pacman package manager, including e.g. vim editor.
The instructions show how to download R and the experimental UCRT toolchain with libraries to build R and R packages.
One can also log in to the machine via graphical interface using a remote desktop client, available for free for both Linux and MacOS. There is a shared folder for transferring files.
Unlike e.g. Docker containers, this is a usual computer intended for interactive use, with state saved on the (virtual) hard disk, which survives across reboots of the virtual machine as well as the host (Linux or macOS) machine. One can create/restore snapshots of that state.
However, one should not save important state on the machine as there is a 90-day limit on use for testing. Please check the license terms when downloading.
The instructions were tested now on Ubuntu 20.04 and macOS 11.2.3.
It is recommended to install the machine only via fast un-metered connection. Expect close to 10G to be downloaded, including the original VM image itself and the toolchain.
Please see the instructions to get started.
The provisioning includes:
setting up SSH: allowing incoming connections, inserting a public key for connecting without a password, starting SSH server on boot
setting up RDP: allowing incoming connections, disabling NLA to allow older clients to connect
installing MSys2, including bash, also with unzip, diffutils, make, winpty, rsync, texinfo, tar, texinfo-tex, zip, subversion, bison, moreutils, xz, patch
installing Inno Setup and MikTeX
Individual provisioning steps are then implemented in PowerShell. Vagrant communicates with the VM using WinRM protocol, which is enabled by default in this VM.
There is the 90-day limit, but even instructions on the background of the VM suggest to re-install after it expires.
Some console applications won’t work from SSH, including MikTeX. Hence, one cannot build the R installer from the SSH connection. However, one can still build R and probably most R packages.
Some R operations on Windows use graphical interface by default. When
working from SSH, one can sometimes disable that, e.g.
options(menu.graphics=FALSE) before installing packages.
The machine is set up for simplicity, not security. The intended use is
notebooks or single-user workstations running inside a trusted home/office
network, ideally still with a firewall on the machine, used for testing and
debugging R packages. See comments in the
Vagrantfile for details.
The version of Windows 10 in this machine is so old that R cannot use UTF-8 as the native encoding. It is still good for testing packages with the UCRT toolchain, many potential issues would not be encoding-related. Also, the current CRAN checks run with Latin 1 encoding as well.
Setting up a virtual machine to check R packages. Instructions to set up and use the VM. Including the experimental UCRT build of R and toolchain, but  has additional details on that.
Howto: UTF-8 as native encoding in R on Windows. Instructions for the experimental UCRT build of R and toolchain.