What kind of testing framework is used for clang OpenMP support?

In test files for OpenMP in clang, you can find code like:

// omp4-error@+2 
  #pragma omp parallel for
    for (auto &item : a) {
      item = item + 1;
    }

From what I understand, it's supposed to catch a certain error message that clang emits.

What testing framework is this and where kind I find more information about it?