add test for unit test that depends on ephemeral model

[MichelleArk]

Add testing for documented workaround to testing a model that depends on an ephemeral model

documentation: https://github.com/dbt-labs/docs.getdbt.com/pull/5281/files#diff-93cd3964ff9d3a505e3620438d7b0594b473f47a26cec74e57d3c24e36df1a24R283

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX
• This PR includes type annotations for new and modified functions

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.12%. Comparing base (86b349f) to head (b718c54).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9929      +/-   ##
==========================================
- Coverage   88.17%   88.12%   -0.05%     
==========================================
  Files         180      180              
  Lines       22578    22578              
==========================================
- Hits        19908    19897      -11     
- Misses       2670     2681      +11     

Flag	Coverage Δ
integration	85.43% <ø> (-0.13%)	⬇️
unit	62.08% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[gshank]

Looks so simple :)