Tests are an important part on preventing regressions and covering new feature functionality. There are multiple ways to run CIR tests.
The more aggresive (slower) one:
$ ninja check-all
CIR specific test targets using ninja:
$ ninja check-clang-cir $ ninja check-clang-cir-codegen
lit from build directory:
$ cd build $ ./bin/llvm-lit -a ../clang/test/CIR