test: Add new behavioral test

[sjrl]

Related Issues

Adds a new behavorial test based on this issue https://github.com/deepset-ai/haystack/issues/8389

@silvanocerza this is also fixed by the subgraphs branch.

Note: This test will still fail currently with the subgraphs branch b/c Doc comparison is fragile when Documents have scores. By this I mean a Doc is assigned a float score by the Retriever and the Doc __eq__ method only does an exact comparison. This breaks when comparing floats due to the imprecision with long decimals.

Proposed Changes:

How did you test it?

Notes for the reviewer

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 11051101178

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 90.283%

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Totals
Change from base Build 11035435372:	0.0%
Covered Lines:	7414
Relevant Lines:	8212

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💛 - Coveralls

[silvanocerza]

Integrated this in #8431 with 149f92fc2c64e9521efd21b3b15a58b539772911 and some small fixes with c730077a444e95f62f54709e8bc017cadb8783ca.