Testing instructions in CONTRIBUTING.md are incorrect/incomplete

[samsrabin]

The instructions here in CONTRIBUTING.md fail, seemingly for a few reasons:

1. The tests look for a config_files.xml file in the parent directory of the CIME checkout. Doing export CIME_MODEL=cesm before testing resolves it, but...
2. ...It then fails because it's looking for a ccs_config/ directory in the CIME checkout's parent.

From the testing GitHub Workflow, it looks like the CIME tests need to be run within a model checkout with the ccs_config submodule loaded.

Even then, I got 57 failures and 28 skips.

Ideally, CIME would have its own ccs_config checkout within each CIME/data/config/$MODEL/ directory that could be used. Barring that, it would be good to update the instructions to say that the testing will only work within a model checkout.

If the latter solution is preferred, I can do it in a PR I'm working on now.

[samsrabin]

Additional things I tried:

• Based on the testing Workflow: export CIME_MODEL="cesm"; export CIME_DRIVER="nuopc"; export SKIP_ENTRYPOINT="true"
• ./bin/git-fleximod update cmeps
• ./bin/git-fleximod update cdeps

That at least fixed most of the unit tests, but everything in test_unit_system_tests_mvk.py got skipped and there's one failure:

================================================================== FAILURES ===================================================================
_________________________________________ TestUnitXMLMachines.test_get_resolved_environment_variable __________________________________________

self = <CIME.tests.test_unit_xml_machines.TestUnitXMLMachines testMethod=test_get_resolved_environment_variable>

    def test_get_resolved_environment_variable(self):
        self.machine.set_machine("multi-compiler")

        assert os.environ["HOME"] == self.machine._get_resolved_environment_variable(
            "$ENV{HOME}"
        )
        assert "" == self.machine._get_resolved_environment_variable("")

        pattern = r"Failed to resolve '\$SHELL{\./xmlquery MODEL}' with: ERROR: Command: '\./xmlquery MODEL' failed with error '/bin/sh: 1: \./xmlquery: not found' from dir '.*/cime'"
        output = self.machine._get_resolved_environment_variable(
            "$SHELL{./xmlquery MODEL}"
        )

>       assert re.match(pattern, output) is not None
E       assert None is not None
E        +  where None = <function match at 0x147c5b931bc0>("Failed to resolve '\\$SHELL{\\./xmlquery MODEL}' with: ERROR: Command: '\\./xmlquery MODEL' failed with error '/bin/sh: 1: \\./xmlquery: not found' from dir '.*/cime'", "Failed to resolve '$SHELL{./xmlquery MODEL}' with: ERROR: Command: './xmlquery MODEL' failed with error '/bin/sh: ./xmlquery: No such file or directory' from dir '/glade/work/samrabin/cime_safe_copy-202602/cime'")
E        +    where <function match at 0x147c5b931bc0> = re.match

CIME/tests/test_unit_xml_machines.py:256: AssertionError
=========================================================== short test summary info ===========================================================
FAILED CIME/tests/test_unit_xml_machines.py::TestUnitXMLMachines::test_get_resolved_environment_variable - assert None is not None
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
============================================ 1 failed, 331 passed, 13 skipped in 70.86s (0:01:10) =============================================

But lots of system tests are still failing.

[jasonb5]

Thanks for point the issue with the testing instructions in CONTRIBUTING.md. I will update this as it should be pointing to the documentation instructions so we can maintain a single source of truth (I'm updating the testing instructions in another PR #4929 ).

The test_unit_system_tests_mvk.py test only runs when the model is E3SM, if this is something CESM would like, it can be enabled.

The failing system tests are being address in #4929.