test: add additional unit tests for Jinja2 Chat Extension

[anakin87]

Related Issues

Investigating on #10429, I found out that we already have "support" for extended ToolCallResult in Jinja2 ChatMessage extension.

Support is basic, as you can see in the new test I added.

I can also imagine something more advanced but I cannot find a use case where this would be helpful.
So @sjrl if you agree, I'd close the original issue.

Proposed Changes:

• add additional unit tests for Jinja2 Chat Extension (and increase coverage a little bit 🙂 )

How did you test it?

CI

Checklist

• I have read the contributors guidelines and the code of conduct.
• I have updated the related issue with new insights and changes.
• I have 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: and added ! in case the PR includes breaking changes.
• I have documented my code.
• I have added a release note file, following the contributors guidelines.
• I have run pre-commit hooks and fixed any issue.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

1 Skipped Deployment

Project	Deployment	Review	Updated (UTC)
haystack-docs	Ignored	Preview	Jan 22, 2026 4:40pm

[coveralls]

Pull Request Test Coverage Report for Build 21256650479

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.007%) to 92.489%

---

Totals
Change from base Build 21256644287:	0.007%
Covered Lines:	14776
Relevant Lines:	15976

---

💛 - Coveralls