Unit-testing MPI Programs with gtest

Question

I'm parallelizing an already existent application that uses gTest with MPI. In MPI programs, the first thing to do is to initialize the environment with a call to

MPI_Init( int *argc, char ***argv )

At the end of an MPI program the root process should also call MPI_Finalize. How can I write unit-tests for such an application using Google Test?

In particular, how do I access argc, and argv from the tests before gTest modifies them.

Right now I'm doing:

int argc = 0;
char** argv = NULL;
boost::mpi::environment env(argc,argv);

TEST(component_test, test_name) {
  // stuff using mpi
}

and feels wrong.

Anecdotal

Answer 1

Are you sure you want to access the argc and argv values before googletest? They are modified to remove googletest specific arguments such as --gtest_filter so that the application does not see them.

I think what you want to do is simply using the following snippet as your main:

int main(int argc, char* argv[]) {
    int result = 0;

    ::testing::InitGoogleTest(&argc, argv);
    MPI_Init(&argc, &argv);
    result = RUN_ALL_TESTS();
    MPI_Finalize();

    return result;
}

Haunted

Thanks! Does InitGoogleTest remove arguments that are not relevant to gTest? – Anecdotal

No, it doesn't. Only the gtest arguments. – Haunted

Answer 2

Just add to @rmhartog's answer.

You probably also want to add below to leave only one listener for printing before RUN_ALL_TESTS(), otherwise, the stdout messages mingle.

::testing::TestEventListeners& listeners =
    ::testing::UnitTest::GetInstance()->listeners();
if (world.rank() != 0) {
    delete listeners.Release(listeners.default_result_printer());
}

Virilism