Issue 11: test reordering

[katrinabrock]

This makes some progress toward:
https://github.com/livingingroups/travelpaths-devel/issues/137 (private repo) aka #11 .

Loosely based on: https://github.com/livingingroups/travelpaths-devel/pull/206

Hopefully this makes it more clear what I mean by adding tests with unordered tf to existing tests rather than creating a new "order tests" file.

[github-actions]

🦺 Coverage summary

🟢 Merging PR #13 (bb53f99) into main (cb5908a) will increase overall coverage by 0.3 percentage points.
🟢 Diff coverage is 92.7% (38 out of 41 modified lines are covered by tests).

Details

Files with changes in coverage

File name	Coverage head	Coverage base	Δ
R/auxiliary.R	81.5%	72.2%	9.3	⬆️
R/backtransform.R	88.6%	89.6%	-1.0	⬇️
Overall	88.1%	87.8%	0.3	⬆️

Coverage for modified lines

File name	Lines modified	Lines tested	Coverage	Missing
R/backtransform.R	39	36	92.3%	130, 131, 133
R/plot.R	2	2	100%
Total	41	38	92.7%

♻️ Comment updated with the latest results.

^{Created on 2026-06-15 with covr2gh v0.0.0.9039.}

[rhirk]

looks good, apart from the conflict in backtransform.R