[WIP, POC] Tests for Interactive TX

[optout21]

Based on: #2419
W-i-P, submitted to see tests & coverage.

[codecov-commenter]

Codecov Report

Patch coverage: 76.21% and project coverage change: -0.09% ⚠️

Comparison is base (61d896d) 90.59% compared to head (deca874) 90.50%.
Report is 17 commits behind head on main.

❗ Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the GitHub App Integration for your organization. Read more.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2541      +/-   ##
==========================================
- Coverage   90.59%   90.50%   -0.09%     
==========================================
  Files         110      111       +1     
  Lines       57410    57917     +507     
  Branches    57410    57917     +507     
==========================================
+ Hits        52008    52416     +408     
- Misses       5402     5501      +99     

Files Changed	Coverage Δ
lightning/src/ln/mod.rs	96.15% <ø> (ø)
lightning/src/ln/msgs.rs	85.82% <0.00%> (ø)
lightning/src/ln/interactivetxs.rs	76.84% <76.84%> (ø)
lightning/src/util/ser.rs	86.12% <100.00%> (+0.84%)	⬆️

... and 19 files with indirect coverage changes

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

[ariard]

Don’t hesitate to propose tests if they can be generalized out of LDK as test vectors addendum for lightning/bolts#851 There is a matrix of test cases with channel type, and I’m not even sure dual funding / splicing are fleshed enough on this.

[optout21]

Patch coverage 76% -- with only a handful of tests and zero negative tests it seems to-good-to-be-true

[optout21]

Closing for now, interactive TX code is still work-in-progress