test: Split test-aaa-auto.R into one generated file per impl category, checked in CI

.github/workflows/custom/after-install/action.yml

@@ -25,6 +25,13 @@ runs:
         fi
       shell: bash
 
+    # Every impl's tests sit in test-aaa-<category>.R, mirroring the
+    # R/aaa-<category>.R that defines the impl
+    # (handbook/testing/suite/). Fails when a rerun would move a test.
+    - name: Check that impl tests sit in their category's file
+      run: Rscript tools/split-aaa-tests.R --check
+      shell: bash
+
     # The roclet that links the C manual from the reference pages, named in
     # DESCRIPTION's Roxygen field, is vendored in tools/igraph.r2cdocs
     # (handbook/architecture/r-layer/documentation/). Only the smoke test

DESCRIPTION

@@ -91,7 +91,7 @@ Config/comment/Needs/roxygen2: The roclet igraph.r2cdocs::docs_rd that
 Config/Needs/website: here, readr, tibble, xmlparsedata, xml2
 Config/testthat/edition: 3
 Config/testthat/parallel: true
-Config/testthat/start-first: aaa-auto, vs-es, scan, vs-operators, weakref,
+Config/testthat/start-first: aaa-*, vs-es, scan, vs-operators, weakref,
     watts.strogatz.game
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE, roclets = c("collate", "namespace",

handbook/architecture/r-layer/new-functions/README.md

@@ -12,5 +12,5 @@ What a new exported function needs before it merges.
   [`tools/AGENTS.md`](/tools/AGENTS.md) is the implementation guide.
 
 A function exported from the C library is generated, never written by hand ([`stimulus/`](/handbook/architecture/stimulus/README.md)):
-its `*_impl()` gets a test in `tests/testthat/test-aaa-auto.R`,
+its `*_impl()` gets a test in `tests/testthat/test-aaa-<category>.R` ([the suite](/handbook/testing/suite/README.md)),
 and a graph constructor prefers `GATTR` and `GATTR-PARAM` in the Stimulus definitions over assigning attributes by hand.

handbook/testing/suite/README.md

@@ -3,7 +3,10 @@
 The testthat suite under `tests/testthat/`.
 
 * A test file mirrors its source file: `R/name.R` is tested in `tests/testthat/test-name.R`.
-* New functionality comes with tests; a new generated `*_impl()` gets one in `test-aaa-auto.R`.
+* New functionality comes with tests; a new generated `*_impl()` gets one in `test-aaa-<category>.R`,
+  the file mirroring the `R/aaa-<category>.R` that defines it.
+  [`tools/split-aaa-tests.R`](/tools/split-aaa-tests.R) moves each impl's tests and snapshots to that file,
+  so rerun it after an impl changes category; CI runs it with `--check` and fails while a test sits elsewhere.
 * `testthat::test_local(reporter = "check")` runs the suite, and `filter = "name"` one file of it;
   `devtools::check()` is the final step before a change is done.