test_runner: add t.assert.fileSnapshot()

[cjihrig]

This commit adds a t.assert.fileSnapshot() API to the test runner. This is similar to how snapshot tests work in core, as well as userland options such as toMatchFileSnapshot().

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[codecov]

Codecov Report

Attention: Patch coverage is 94.68085% with 5 lines in your changes missing coverage. Please review.

Project coverage is 89.17%. Comparing base (dc5d0f9) to head (e80cc64).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/test_runner/snapshot.js	94.25%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #56459   +/-   ##
=======================================
  Coverage   89.16%   89.17%           
=======================================
  Files         662      662           
  Lines      191668   191731   +63     
  Branches    36884    36894   +10     
=======================================
+ Hits       170908   170967   +59     
+ Misses      13621    13620    -1     
- Partials     7139     7144    +5     

Files with missing lines	Coverage Δ
lib/internal/test_runner/test.js	96.93% <100.00%> (+<0.01%)	⬆️
lib/internal/test_runner/snapshot.js	98.04% <94.25%> (-1.96%)	⬇️

... and 25 files with indirect coverage changes

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/64330/

[mcollina]

lgtm

I think adding a base path that's going to be applied to all non-absolute paths would be cool. Something like require('node:test').setFileSnapshotDir('/my/path').

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/64343/ 🟡

[cjihrig]

That would be easy to implement. My only concern would be that we already have snapshot. setResolveSnapshotPath() for customizing the location of regular snapshot files. I don't think that API would work well for this use case. That API is intended to map a test file to a path that will contain multiple snapshots. For this use case, we need something very different. I guess a separate API for that wouldn't be the end of the world though.

[cjihrig]

Rebased due to conflicts. Approval/re-approval requested.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/64412/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/64420/

[nodejs-github-bot]

Landed in 19c8cc1