rocs```, two ```int``` giving respectively the rank of the current process and the size of the communicator for ```test_comm```. These last two are just here for convenience and could be retrieved from ```test_comm```.

We always have:

```
MPI_TEST_CASE("my_test",N) {
  CHECK( test_nb_procs == N );
  MPI_CHECK( i, test_rank==i ); // for any i<N
}
```

### Assertions
It is possible to use regular assertions in an ```MPI_TEST_CASE```. MPI-specific assertions are also provided and are all prefixed with ```MPI