Tests and cleanup for #610 (output_variables fallback behavior)

[mattw-nws]

[Short description explaining the high-level reason for the pull request]

Additions

• Two tests for invalid entries in output_variables

Removals

• Obsolete fallback condition code in Bmi_Multi_Formulation.cpp

Changes

Testing

Screenshots

Notes

Todos

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

Testing checklist (automated report can be put here)

Target Environment support

• Linux

[mattw-nws]

As a side note, the test logic in Bmi_Multi_Formulation_Test.cpp is probably overengineered at this point... we need tests to make sure the test code produces what it's supposed to. Seems like there should be an easier way.

[stcui007]

I only have some rather trivial comments. On line 486 of Bmi_Multi_Formulation_Test.cpp, the comment line, the number of example scenarios should now be 6?

In the same file, line 635-636, it is probably better to remove one of the empty lines.

[PhilMiller]

Looks fine to me.

[stcui007]

The new change makes the codes in the function more generalized. Looks good to me.