First steps in implementing a unit test for OASISCoupledOcean

A skeleton of a unit test in OASISCoupledOcean_test.cpp and some changes
 in the accompanying CMakeLists.txt to make it compile. Added
 MainMPI.cpp so that the test starts. We still need a namcouple file and
  the actual ins-and-outs of the test.

physics/test/CMakeLists.txt

@@ -37,6 +37,12 @@ if(ENABLE_MPI)
         PRIVATE USE_MPI TEST_FILES_DIR=\"${CMAKE_CURRENT_SOURCE_DIR}\"
     )
     target_link_libraries(testTOPAZOcn_MPI1 PRIVATE nextsimlib doctest::doctest)
+    if (ENABLE_OASIS)
+        add_executable(testOASISCoupledOcean_MPI2 "OASISCoupledOcean_test.cpp" "MainMPI.cpp")
+        target_include_directories(testOASISCoupledOcean_MPI2 PRIVATE "${ModulesRoot}/OceanBoundaryModule")
+        target_compile_definitions(testOASISCoupledOcean_MPI2 PRIVATE TEST_FILES_DIR=\"${CMAKE_CURRENT_SOURCE_DIR}\")
+        target_link_libraries(testOASISCoupledOcean_MPI2 PRIVATE nextsimlib doctest::doctest)
+    endif ()
 else()
     add_executable(testERA5Atm "ERA5Atm_test.cpp")
     target_compile_definitions(testERA5Atm PRIVATE TEST_FILES_DIR=\"${CMAKE_CURRENT_SOURCE_DIR}\")

physics/test/MainMPI.cpp

@@ -0,0 +1,30 @@
+/*!
+ * @file MainMPI.cpp
+ *
+ * @date 13 Sep 2024
+ * @author Einar Ólason <einar.olason@nersc.no>
+ *
+ * This file is required so that the MPI enabled doc-test OASISCoupledOcean_test.cpp (and any
+ * others) can run.
+ */
+
+#define DOCTEST_CONFIG_IMPLEMENT
+
+#include <doctest/extensions/doctest_mpi.h>
+
+int main(int argc, char** argv)
+{
+    doctest::mpi_init_thread(argc, argv, MPI_THREAD_MULTIPLE);
+
+    doctest::Context ctx;
+    ctx.setOption("reporters", "MpiConsoleReporter");
+    ctx.setOption("reporters", "MpiFileReporter");
+    ctx.setOption("force-colors", true);
+    ctx.applyCommandLine(argc, argv);
+
+    int test_result = ctx.run();
+
+    doctest::mpi_finalize();
+
+    return test_result;
+}

physics/test/OASISCoupledOcean_test.cpp

@@ -0,0 +1,40 @@
+/*!
+ * @file OASISCoupledOcean_test.cpp
+ *
+ * @date 13 Sep 2024
+ * @author Einar Ólason <einar.olason@nersc.no>
+ */
+
+#include <doctest/extensions/doctest_mpi.h>
+
+#include "include/OASISCoupledOcean.hpp"
+
+namespace Nextsim {
+
+TEST_SUITE_BEGIN("OASISCoupledOcean");
+MPI_TEST_CASE("OASIS init put and get", 2)
+{
+    MPI_Comm modelCommunicator;
+    int compID; // Not actually used. Only useful for debugging
+    const std::string compName = "nextsim"; // Not useful for any setups we have in mind
+    OASIS_CHECK_ERR(oasis_c_init_comp(&compID, compName.c_str(), OASIS_COUPLED));
+    OASIS_CHECK_ERR(oasis_c_get_localcomm(&modelCommunicator));
+
+    ModelArray::setDimensions(ModelArray::Type::H, { 1, 1 });
+    ModelArray::setDimensions(ModelArray::Type::Z, { 1, 1, 1 });
+
+    HField cice(ModelArray::Type::H);
+    cice = 1.0;
+    ModelComponent::getStore().registerArray(Protected::C_ICE, &cice, RO);
+    OASISCoupledOcean ocpl;
+    ModelMetadata metadata;
+
+    ocpl.setData(ModelState::DataMap());
+    ocpl.setMetadata(metadata);
+    ocpl.updateBefore(TimestepTime());
+    ocpl.updateAfter(TimestepTime());
+
+    OASIS_CHECK_ERR(oasis_c_terminate());
+}
+TEST_SUITE_END();
+}