How to add CppUnitTest.h to Visual C++ installation?

We’re being forced to update the existing VS2017 install to VS2019, and one thing continues to break in the builds, as the compiler cannot find the CppUnitTest.h anywhere.

Indeed, the full search of the filesystem comes up with nothing — is it part of some optional component installable with the Visual Studio Installer? There are plenty of manuals, such as Microsoft’s own, explaining, how to use the testing framework, but none detailing, how to install it…