Add API test suites

[samhatfield]

Currently we have the following tests in ecTrans:

• ectrans_test_install: test whether a program can be built against ecTrans
• ectrans_test_setup_trans0: a basic test for setup_trans0 with one fixed set of arguments
• ectrans_test_adjoint: a high-level test of the tangent-linear/adjoint correspondence of INV_TRANS, INV_TRANSAD, DIR_TRANS, DIR_TRANSAD, all in one
• Separate tests of tangent-linear/adjoint correspondence of INV_TRANS/AD and DIR_TRANS/AD
• A test of tangent-linear/adjoint correspondence of GPNORM_TRANSTL/AD
• Tests of ecTrans global and LAM transforms under many settings, using the benchmark program. These are sort of integration tests
• transi tests

I propose to add a mechanism for unit tests, by which I mean specifically an isolated test for a single feature of one of the ecTrans subroutines. I suggest to focus on the external subroutines (at least for now). These tests will complement the tests above, and in some cases possibly replace them (e.g. we won't need ectrans_test_setup_trans0 anymore, and the benchmark program could perhaps finally be repurposed for what it was built for - benchmarking).

This draft PR gives an idea of how this could be achieved in vanilla CMake. I have followed this example. Here is how it works:

• There is a new directory: tests/unit.
• In this directory we have a directory for each external subroutine (currently just setup_trans0 and setup_trans).
• In each of these, we write a plain old Fortran module with a INTEGER FUNCTION for each unit test. These all are named UNIT_TEST_*. Each function carries out a unit test and returns 0 for success or 1 for failure. They all have BIND(C) specified so they can be called from a C function linked into the final executable.
• In the CMakeLists.txt file for this suite, we define again the tests in the corresponding Fortran file in a list.
• Using create_test_sourcelist we create a C program which provides a callable wrapper for each of the Fortran unit tests. From this we create an executable which CTest can call.
• We then add each unit test one by one so CTest is aware of them, using our C program as the test executable.

The above logic is repeated for each enabled precision.

All unit tests will then be visible when running ctest -R unit_test.

Here are the tests I've implemented so far:

➜  build ctest -N -R unit_test
Test project /Users/samhatfield/Work/ECMWF/ectrans/build
  Test #188: unit_test_setup_trans0_eq_regions_dp
  Test #189: unit_test_setup_trans0_eq_regions_sp
  Test #190: unit_test_setup_trans_without_setup_trans0_dp
  Test #191: unit_test_setup_trans_basic_dp
  Test #192: unit_test_setup_trans_odd_ndgl_dp
  Test #193: unit_test_setup_trans_octahedral_dp
  Test #194: unit_test_setup_trans_stretching_dp
  Test #195: unit_test_setup_trans_all_fftw_dp
  Test #196: unit_test_setup_trans_belusov_dp
  Test #197: unit_test_setup_trans_flt_dp
  Test #198: unit_test_setup_trans_without_setup_trans0_sp
  Test #199: unit_test_setup_trans_basic_sp
  Test #200: unit_test_setup_trans_odd_ndgl_sp
  Test #201: unit_test_setup_trans_octahedral_sp
  Test #202: unit_test_setup_trans_stretching_sp
  Test #203: unit_test_setup_trans_all_fftw_sp
  Test #204: unit_test_setup_trans_belusov_sp
  Test #205: unit_test_setup_trans_flt_sp

Total Tests: 18

I have implemented a "will fail" logic to handle cases that are expected to fail (e.g. calling SETUP_TRANS without SETUP_TRANS0 or initialising with an odd number of latitudes - both cases above). However this will require modifying the abort behaviour of SDL_SRLABORT: we need to somehow disable the raising of SIGABRT and use ERROR STOP instead of STOP so an error code 1 is returned. Otherwise I don't think there's any way to recover from ABORT_TRANS.

Also, for now I've disabled MPI in these tests. We obviously need to test at least some of the subroutines with MPI enabled (e.g. DIST_GRID) but I'm not sure how to do this yet without wrapping the whole suite in a for loop over 0, 1, 2 MPI tasks and having the number of tests exploding.

Anyway, any thoughts @wdeconinck @marsdeno @ddegrauwe @dhaumont @RyadElKhatibMF?

[samhatfield]

Ninja doesn't like the fact that I generate the same Fortran modules twice. Need to find a way to have a precision-qualified module file emitted when each test suite is compiled.

[dhaumont]

Very nice initiative.
On top of what you describe, we also need to think about:

• testing for GPU and CPU
• test for different grid partitionning (this is probably linked to MPI)
• test the new field-api interface
• cover the LAM

[samhatfield]

Very nice initiative. On top of what you describe, we also need to think about:

• testing for GPU and CPU
• test for different grid partitionning (this is probably linked to MPI)
• test the new field-api interface
• cover the LAM

Thanks! Yes good points.

• CPU and GPU should be straightforward - basically following the same logic as the precisions.
• Different grid partitioning - you mean like different NPROMA values?
• Yup, should be straightforward to add those tests.
• Yeah I thought maybe you and Daan could add a tests/etrans/unit directory which mirrors the test/trans/unit one.

[samhatfield]

Discussions with @marsdeno highlighted that what I've done here is not really "unit tests". A better name would be "interface tests".

[samhatfield]

I have renamed the "unit" tests to "API" tests.

[samhatfield]

PR reduced in scope to only include new testing infrastructure and test suite (actually just a single test) for SETUP_TRANS0.