EkatCreateUnitTest vs CreateUnitTest

[jaelynlitz]

Even when not using MPI, calling EkatCreateUnitTest vs CreateUnitTest causes different behavior when you have additional libraries to link against.

For example in mam4xx, tests that include and use atmosphere_utils.hpp will throw an undefined reference error when set with CreateUnitTest in the cmake as below, but work when used with EkatCreateUnitTest

CreateUnitTest(mam4_ndrop_unit_tests ndrop_unit_tests.cpp)
vs
EkatCreateUnitTest(mam4_ndrop_unit_tests ndrop_unit_tests.cpp LIBS mam4xx_tests ${HAERO_LIBRARIES})

Should just one of these macros be used as default? Does not using mpi in mam4xx change that choice? Issue open for discussion...

cc @jeff-cohere

[jeff-cohere]

Personally, I think we should just use EkatCreateUnitTest. We created CreateUnitTest when Haero was going to be the aerosol package, and now we have Haero and mam4xx, so we don't have a single context with all the information about which libraries to link in.

@overfelt , @pbosler what do you think about this?

[overfelt]

It seems CreateUnitTest time has passed.

[pbosler]

I like having just one; EKAT's version is good for me.

[jeff-cohere]

Okay, it sounds like we should decommission CreateUnitTest. @jaelynlitz , if you proceed to use EkatCreateUnitTest for your work, I'll set up a PR that gets rid of CreateUnitTest and expunges it from Haero. I think we'll probably need a related PR to switch off of CreateUnitTest in mam4xx first, though.

@pressel @odiazib @mjs271 @CameronRutherford

[cameronrutherford]

I approve of ditching CreateUnitTest for a standardized EkatCreateUnitTest, but I want to make sure the change in behaviour is clear:

# 1 ---
# This does not link against mam4xx_tests or ${HAERO_LIBRARIES}
CreateUnitTest(mam4_ndrop_unit_tests ndrop_unit_tests.cpp)
target_link_libraries(mam4_ndrop_unit_tests PRIVATE mam4xx_tests ${HAERO_LIBRARIES})
# 2 ---
# This links against additional libraries
EkatCreateUnitTest(mam4_ndrop_unit_tests ndrop_unit_tests.cpp LIBS mam4xx_tests ${HAERO_LIBRARIES})

1 links against the additional libraries manually, whereas 2 links against the extra libraries through the single CMake macro call. With the additional call to target_link_libraries, I think the behaviour should be identical.

I am sure we could also make our own mam4xx_add_test macro, but I think the EKAT one serves us just fine here.

[jeff-cohere]

That's correct, Cameron. CreateUnitTest is just a thin wrapper around EkatCreateUnitTest anyway, and we don't have the information we need in Haero to make decisions about which libraries to link against testing executables within mam4xx.