Tests: line-tables-only dev debuginfo, nextest GPU group, faster loop docs (#2204) (#2414)

- [profile.dev] debug = "line-tables-only", matching CI's CARGO_PROFILE_DEV_DEBUG; halves link
  time and PDB size for test binaries.
- .config/nextest.toml: optional cargo-nextest runs with the GPU tests capped at 4 concurrent
  processes (unlimited ones time out in wgpu).
- AGENTS.md / docs/development.md: iteration commands (--lib --tests, --test <file>, nextest,
  doctests separately). CI is unchanged.

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>

.config/nextest.toml

@@ -0,0 +1,15 @@
+# cargo-nextest (https://nexte.st): runs every test in its own process, in parallel across test
+# binaries. Optional for local runs; `cargo test` keeps working and stays what CI runs (#2204).
+#
+#   cargo nextest run --workspace        # all tests except doctests
+#   cargo test --doc --workspace         # nextest does not run doctests
+#
+# GPU tests: each test is its own process here, so the in-process `gpu_lock()` mutexes no longer
+# serialize them. Too many concurrent wgpu devices time out (`PollError: ... Wait timed out`), so
+# this group caps them at 4.
+[test-groups]
+gpu = { max-threads = 4 }
+
+[[profile.default.overrides]]
+filter = 'package(photocraft-gpu) | (package(photocraft-ui-egui) & (kind(test) | test(/canvas|gpu|mip|type_tool/)))'
+test-group = 'gpu'

AGENTS.md

@@ -99,6 +99,8 @@ cargo xtask perf --quick    # if you touched a hot path; `cargo xtask perf --upd
 cargo xtask test-corpus     # if you touched psd, io, codecs, compose, gpu, text or format (or: --changed decides)
 ```
 
+While iterating, run less and keep the full commands above as the final gate: `cargo test -p <crate> --lib --tests` skips the examples and doctests plain `cargo test` builds every time (ui-egui has 11 examples), and `cargo test -p <crate> --test <file>` runs one integration-test file. `cargo nextest run` runs tests in parallel across binaries; see `docs/development.md` › Faster test loops.
+
 **Test corpora.** Real-file corpora live in `corpus/` (gitignored, never committed), fetched at pinned commits and sha256-verified by `cargo xtask corpus --all`: our Photoshop-authored oracles from https://github.com/storytold/photocraft-corpus plus psd-tools, ag-psd and PngSuite from their upstreams. Pins: `xtask/src/corpus_pins.rs`. The corpus tests are opt-in (cargo feature `corpus`): plain `cargo test` skips them, and with the feature on a missing corpus fails ("run `cargo xtask corpus --all`"). `cargo xtask test-corpus` fetches and runs them all. CI always runs them (the `corpus` job, cached by pin). Never commit corpus files; new oracles go to photocraft-corpus (its `AGENTS.md`), then a pin bump here. Details: `docs/development.md` › Test corpora.
 
 Commands must **never panic** on bad input (Rule 9): every `run` closure and the code it calls returns `Err`, not a panic, for any params or document state. New commands come with a graceful-failure test (empty/out-of-range/wrong-type params → `Err`, not a crash).

Cargo.toml

@@ -69,6 +69,10 @@ opt-level = 2
 
 [profile.dev]
 opt-level = 1
+# Line tables keep file:line in panic backtraces but drop variable info, which roughly halves link
+# time and PDB size for the ~260 test binaries (#2204). CI sets the same through
+# CARGO_PROFILE_DEV_DEBUG. To inspect locals in a debugger, build with CARGO_PROFILE_DEV_DEBUG=true.
+debug = "line-tables-only"
 
 [profile.release]
 lto = "thin"

docs/development.md

@@ -42,6 +42,21 @@ cargo xtask parity                                         # Photoshop menu cove
 
 Image code is slow at `opt-level 0`, so the workspace profile builds dependencies at `opt-level 2`. Use `--release` for anything interactive.
 
+The dev profile builds with `debug = "line-tables-only"`: panic backtraces keep file and line, and test binaries link about twice as fast. To inspect local variables in a debugger, build with `CARGO_PROFILE_DEV_DEBUG=true`.
+
+### Faster test loops
+
+Most of a `cargo test` run is linking test binaries and running them one after another. While iterating:
+
+```sh
+cargo test -p <crate> --lib --tests        # skip examples and doctests (ui-egui has 11 examples)
+cargo test -p <crate> --test <file>        # one integration-test file
+cargo nextest run --workspace              # parallel across binaries (cargo install cargo-nextest --locked)
+cargo test --doc --workspace               # nextest does not run doctests
+```
+
+[cargo-nextest](https://nexte.st) runs each test in its own process. `.config/nextest.toml` puts the GPU tests (`photocraft-gpu`, and ui-egui's integration and canvas/GPU tests) in a group of at most 4 at a time, because each process opens its own wgpu device and the in-process `gpu_lock()` no longer serializes them. On a 32-thread Windows machine the full workspace went from 297 s (`cargo test`) to about 120 s (#2204). Ignored tests run with `cargo nextest run --run-ignored only`. CI still runs `cargo test`, and a full `cargo test` stays the final check before a PR.
+
 ## Fonts (craft-fonts)
 
 Font assets shared by the Crafting Apps live in [storytold/craft-fonts](https://github.com/storytold/craft-fonts), never in this repo: don't commit font files here (Inter and JetBrains Mono in `assets/fonts/` are the only exceptions; new fonts go to craft-fonts). The rules are in `craftrules/standards/fonts.md` in a sibling `craftrules` checkout (see below); that repository is not public, so outside contributors can ask a maintainer for the rules that apply to their change.