fix: small improvement to pipeline v2 tests

[ZanSara]

Related Issues

Small bug found in pair-programming with @vblagoje

Proposed Changes:

• adds a missing return statements
• improves a test to make sure the pipeline returns

How did you test it?

• local tests run

Notes for the reviewer

n/a

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[coveralls]

Pull Request Test Coverage Report for Build 5281330094

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 42.287%

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Files with Coverage Reduction	New Missed Lines	%
preview/pipeline.py	3	90.91%

Totals
Change from base Build 5280122921:	0.0%
Covered Lines:	9543
Relevant Lines:	22567

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💛 - Coveralls