Merge pull request 'Move BASIC fixtures into the editable language corpus' (#42) from 40 into main

Reviewed-on: #42

.gitea/workflows/ci.yaml

@@ -17,7 +17,7 @@ jobs:
           # Not recursive, deliberately. The top-level build needs
           # deps/libakerror and deps/libakstdlib, via add_subdirectory, and
           # nothing else: the golden corpus and the Commodore font now live in
-          # this repository (tests/reference/ and assets/fonts/), so
+          # this repository (tests/language/ and assets/fonts/), so
           # deps/basicinterpret is no longer a build dependency at all.
           # It does *not* need deps/libakgl, which is guarded behind
           # AKBASIC_WITH_AKGL and defaults OFF -- and recursing into it would
@@ -62,11 +62,9 @@ jobs:
         run: |
           cmake -S . -B build
           cmake --build build --parallel 2
-      # The suite is 78 cases: 41 golden files byte-compared against the Go
-      # reference's own corpus (checked in at tests/reference/, see its README),
-      # 9 local golden cases for verbs the reference never implemented, 25 unit
-      # tests, 2 embedding examples, and 1 known-failing test that asserts the
-      # *correct* contract for defects carried over from the reference (TODO.md
+      # The suite is 112 cases: 65 language files with sibling expectations,
+      # 43 unit tests, 3 embedding examples, and docs_examples.
+      # Some unit tests assert the *correct* contract for known defects (TODO.md
       # section 6). A green run therefore does not mean defect-free -- see
       # AKBASIC_KNOWN_FAILING_TESTS.
       #

CLAUDE.md

@@ -57,9 +57,9 @@ repeating where you will see them:
   `include/akgl/SDL_GameControllerDB.h`. Change the template or the generator script.
 - **Do not reformat code you are not otherwise changing.** Several files mix tabs and spaces
   and there is no repo-wide formatter; style conversions get their own commit.
-- **Do not edit `tests/reference/`.** Those expectations came from the Go implementation and
-  are never edited to suit this interpreter. A deliberate divergence goes in
-  `tests/reference/README.md`'s divergence table and `docs/13-differences.md`.
+- **Keep `tests/language/` editable.** Its `.bas` programs and sibling `.txt` expectations
+  are changed together when behavior changes. Record deliberate language decisions in
+  `TODO.md` or `docs/13-differences.md`.
 - **Open an issue for outstanding work; do not add it to `TODO.md`.**
   <https://source.starfort.tech/andrew/akbasic/issues>, or `tea issues create --repo
   andrew/akbasic`. Name the file and line, the functional consequence, and what closing it would

CMakeLists.txt

@@ -448,7 +448,7 @@ if(AKBASIC_WITH_AKGL)
   # against.
   #
   # **A byte comparison of a rendered PNG is a deliberate bet**, the same bet
-  # tests/reference/ already makes about golden output: that the dummy video
+  # the language corpus makes about golden output: that the dummy video
   # driver and the software renderer are reproducible. They are, run to run and
   # build to build. What is untested is an SDL upgrade that shifts one pixel of
   # a diagonal, and the answer to that is to regenerate the figures in the same
@@ -531,63 +531,20 @@ if(AKBASIC_WILL_FAIL_TESTS OR AKBASIC_KNOWN_FAILING_TESTS)
   )
 endif()
 
-# The reference's own corpus, byte-compared against the sibling .txt. One CTest
-# case per .bas so a failure names the file.
+# The editable language corpus. One CTest case per .bas so a failure names the
+# file. Each program is paired with a sibling .txt expectation; see
+# tests/language/README.md for the editing rule.
 #
-# It used to be driven in place out of deps/basicinterpret, on the reasoning that
-# copying a submodule's corpus guarantees drift. That reasoning was sound and it
-# has been overruled deliberately: the Go dependency is being deprecated, and a
-# build that cannot run its acceptance suite without cloning the implementation
-# it replaced is not finished. The copy is byte-identical to
-# basicinterpreter@d76162c and tests/reference/README.md records
-# where it came from and what the drift now costs.
-file(GLOB_RECURSE AKBASIC_GOLDEN_CASES
-  RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}/tests/reference"
-  "${CMAKE_CURRENT_SOURCE_DIR}/tests/reference/*.bas"
-)
-
-foreach(_case IN LISTS AKBASIC_GOLDEN_CASES)
-  string(REGEX REPLACE "^tests/" "" _name "${_case}")
-  string(REGEX REPLACE "\\.bas$" "" _name "${_name}")
-  string(REPLACE "/" "_" _name "${_name}")
-  _add_test(
-    NAME golden_${_name}
-    COMMAND ${CMAKE_COMMAND}
-            -DBASIC=$<TARGET_FILE:basic>
-            -DCASE=${CMAKE_CURRENT_SOURCE_DIR}/tests/reference/${_case}
-            -P ${CMAKE_CURRENT_SOURCE_DIR}/tests/golden.cmake
-  )
-endforeach()
-
-if(AKBASIC_GOLDEN_CASES)
-  set(AKBASIC_GOLDEN_NAMES)
-  foreach(_case IN LISTS AKBASIC_GOLDEN_CASES)
-    string(REGEX REPLACE "^tests/" "" _name "${_case}")
-    string(REGEX REPLACE "\\.bas$" "" _name "${_name}")
-    string(REPLACE "/" "_" _name "${_name}")
-    list(APPEND AKBASIC_GOLDEN_NAMES golden_${_name})
-  endforeach()
-  _set_tests_properties(${AKBASIC_GOLDEN_NAMES} PROPERTIES TIMEOUT 30)
-  # An AKGL build of `basic` opens a window, and forty-one of them is not what
-  # anybody running the suite wanted. The dummy driver produces the same stdout,
-  # which is the only thing a golden case compares.
-  if(AKBASIC_WITH_AKGL)
-    _set_tests_properties(${AKBASIC_GOLDEN_NAMES} PROPERTIES
-      ENVIRONMENT "SDL_VIDEODRIVER=dummy;SDL_AUDIODRIVER=dummy;SDL_RENDER_DRIVER=software")
-  endif()
-endif()
-
-# The local golden corpus, for verbs the reference never implemented.
+# The corpus includes programs carried over from the deprecated Go implementation
+# and cases written for this interpreter. Their provenance is useful when
+# investigating a regression, but it does not make any case immutable.
 #
-# Still separate now that the reference's corpus lives in this repository too,
-# and the reason changed rather than went away: tests/reference/ is a *record* of
-# what the Go implementation did and nothing in it should ever be edited to suit
-# this one, while tests/language/ is ours to change. Registered under local_ so a
-# failure says at a glance which of the two it came from -- and so a diff that
-# touches tests/reference/ stands out as the thing it is.
+# Programs carried over from the deprecated Go implementation and cases written
+# for this interpreter use the same editable `.bas`/`.txt` contract. Registered
+# under local_ so every failure identifies the program that produced it.
 #
 # Note what this can and cannot cover. The graphics and sound verbs draw and play
-# rather than print, so what a golden file sees of them is their *refusals* and
+# rather than print, so what a golden file sees of them is their refusals and
 # whatever a program can PRINT about the state they changed. The behaviour that
 # reaches a device is asserted against tests/mockdevice.h instead.
 file(GLOB_RECURSE AKBASIC_LOCAL_CASES

MAINTENANCE.md

@@ -88,7 +88,7 @@ source stays readable as documentation of what the original did. Neither is bind
 
 **It is not a build or test dependency.** Both configurations have been configured, built and
 run from scratch with it moved out of the tree. Its acceptance corpus is checked in at
-`tests/reference/` and its Commodore font at `assets/fonts/`.
+`tests/language/` and its Commodore font at `assets/fonts/`.
 
 ```sh norun
 cd deps/basicinterpret
@@ -351,15 +351,10 @@ name. That is not cosmetic: `add_executable` creates a dependency's targets even
 
 ### The golden corpora
 
-`tests/reference/` is the Go implementation's own acceptance suite, byte-compared.
-**Nothing in it is ever edited to suit this interpreter.** If a case fails, either this
-interpreter is wrong or the divergence is deliberate — and a deliberate one goes in
-`tests/reference/README.md`'s divergence table and `docs/13-differences.md`, not into the
-expectation file. `tests/reference/README.md`
-says the same thing at more length.
-
-`tests/language/` is ours and may be changed freely. A new language feature needs a
-`.bas`/`.txt` pair there as well as unit tests.
+`tests/language/` is the editable language corpus. It includes cases carried over from the
+deprecated Go implementation as well as cases written for this interpreter. Every `.bas` file
+has a sibling `.txt` expectation, and a new language feature needs that pair as well as unit
+tests. Change both deliberately in the same commit; provenance does not make a case immutable.
 
 ### Mutation-check a fix before you believe it
 

README.md

@@ -10,7 +10,7 @@ implementation that started from the Java Lox instructions in
 [craftinginterpreters.com](https://craftinginterpreters.com) and then struck off on its own. That
 project is deprecated. It is vendored here as the behavioural spec to read when a question about
 semantics comes up, and its acceptance corpus is checked in at
-[`tests/reference/`](tests/reference/README.md) and runs on every build — so nothing about
+[`tests/language/`](tests/language/README.md) and runs on every build — so nothing about
 building or testing this project needs it.
 
 ## Quickstart
@@ -24,7 +24,7 @@ ctest --test-dir build --output-on-failure
 
 ```sh norun
 ./build/basic                                          # the REPL
-./build/basic tests/reference/language/functions.bas   # run a program
+./build/basic tests/language/functions.bas             # run a program
 ```
 
 ```basic
@@ -129,7 +129,7 @@ version are catalogued in [`TODO.md`](TODO.md) and summarised for a BASIC progra
 | [`docs/`](docs/README.md) | The guide: eighteen chapters, the language then each hardware area then a reference section for every verb and function, [Chapter 14](docs/14-architecture.md) on the interpreter's own architecture, [Chapter 15](docs/15-error-codes.md) listing every error code, and [Chapters 17](docs/17-tutorial-breakout.md) and [18](docs/18-tutorial-breakout-artwork.md) building a whole game twice |
 | [`MAINTENANCE.md`](MAINTENANCE.md) | For contributors and maintainers: the documentation-example harness, the three test lists, mutation testing, error-code allocation, style |
 | [`TODO.md`](TODO.md) | Outstanding defects, with file, line and consequence |
-| [`tests/reference/README.md`](tests/reference/README.md) | Where the golden corpus came from, and the rule for changing it |
+| [`tests/language/README.md`](tests/language/README.md) | The editable language corpus and the rule for changing it |
 
 API documentation builds with `doxygen Doxyfile`, into `build/docs/html`.
 

TODO.md

@@ -38,7 +38,7 @@ What it changes:
 - **§1.8's message-text contract is now a convention.** Improving a message is allowed; it costs
   a golden file, which is a cost rather than a veto.
 - **§5's bar drops** from "defensible against the golden suite" to defensible on its own merits.
-- **`tests/reference/` becomes a regression suite rather than a specification.** Diverging from
+- **`tests/language/` is the editable language corpus rather than a protected specification.** Diverging from
   it is allowed and must be deliberate and recorded — see its README.
 
 What it does **not** change:
@@ -306,13 +306,13 @@ to `Println`, which adds another.
 **This used to be a hard contract and is now a default.** The Go implementation is deprecated
 and will not be updated, so the two projects are no longer required to match — see §0.1. What
 survives is the practical half: these strings and this newline behaviour are what every
-expectation in `tests/reference/` was written against, so changing one means changing golden
+expectation in `tests/language/` was written against, so changing one means changing the paired
 files, and that is worth doing on purpose rather than by accident. A message that reads
 awkwardly *may* now be improved; do it deliberately, move the expectations in the same commit,
 and add a line to §5.
 
 Numeric formatting still matches the reference: integers via `%" PRId64 "`, floats via `%f`
-(Go's `%f` and C's `%f` both give six decimals — `tests/reference/language/arithmetic/float.txt`
+(Go's `%f` and C's `%f` both give six decimals — `tests/language/arithmetic/float.txt`
 confirms). No reason to change it, which is different from not being allowed to.
 
 ### 1.9 Which `libakstdlib` calls are cleared for use — **the bans are lifted**
@@ -375,7 +375,7 @@ Phases 0 through 6 of the original plan are done. The interpreter builds clean u
 
 It *did* reproduce the reference byte for byte, and that claim is retired rather than broken:
 §0.1 released it, and one case has since diverged deliberately (§6 item 16, listed in
-`tests/reference/README.md`). Everything else still matches, which is worth knowing but is no
+`tests/language/README.md`). Everything else still matches, which is worth knowing but is no
 longer a gate.
 
 ```sh
@@ -408,17 +408,16 @@ and the only path that existed — `AKBASIC_MODE_RUNSTREAM` reading through the
 is the code the README quotes, built by every build and registered as a CTest case so a
 signature change breaks the build rather than rotting the document.
 
-**The acceptance suite is the reference's own corpus, checked in at `tests/reference/`.** All
-41 `.bas` files are registered as individual CTest cases and byte-compared against their `.txt`
+**The acceptance suite is the editable language corpus, checked in at `tests/language/`.** All
+65 `.bas` files are registered as individual CTest cases and compared against their `.txt`
 — including the trailing double newline on an error line (§1.8).
 
 It was driven *in place* out of `deps/basicinterpret` until 2026-07-31, on the reasoning that
 copying a submodule's corpus guarantees drift. That reasoning was sound and was overruled
 deliberately: the Go dependency is being deprecated, and a build that cannot run its own
 acceptance suite without cloning the implementation it replaced is not finished. The copy is
-byte-identical to `basicinterpreter@d76162c`, and `tests/reference/README.md` records the
-provenance, the cost of the drift nobody is watching for now, and the rule that those
-expectations are never edited to suit this interpreter.
+originally byte-identical to `basicinterpreter@d76162c`, and `tests/language/README.md` records the
+provenance and the rule that programs and expectations are edited together deliberately.
 
 **Nothing in the build or the suite needs `deps/basicinterpret` any more**, and that is checked
 rather than assumed — both configurations were configured, built and run from scratch with the
@@ -1026,7 +1025,7 @@ deviations from the reference's *program*: `main.go` and the SDL half of
 
     **What it costs a program:** a listing that used `INPUT$`, `LEN#` or `GOTO%` as a variable
     stops parsing, and the fix is to rename the variable. One case in the reference's own corpus
-    did exactly that; see `tests/reference/README.md`.
+    did exactly that; see `tests/language/examples/strreverse.bas`.
 
 ### Deviations in statement separation
 
@@ -1391,10 +1390,10 @@ deviations from the reference's *program*: `main.go` and the SDL half of
     **This one moved a golden file.** A line with no number used to be filed under the loader's
     cursor unchanged — that is, on top of the line before it — so two unnumbered lines in a row
     silently lost the first, and a *blank* line erased whatever preceded it. The reference does
-    the same, and `tests/reference/language/arithmetic/integer.bas` is the proof: four `PRINT`
+    the same, and `tests/language/arithmetic/integer.bas` is the proof: four `PRINT`
     statements, an expectation with three values, and a trailing blank line that erased
     `40 PRINT 4 - 2` before the program ran. The expectation is now `4 4 2 2` and
-    `tests/reference/README.md` records it.
+    `tests/language/README.md` records it.
 
     In its place: `akbasic_runtime_file_line()` (`src/runtime.c`) is the one implementation of
     the rule, shared by `akbasic_runtime_load()`, RUNSTREAM and `DLOAD`. A numbered line is
@@ -1586,9 +1585,9 @@ be reproduced before it can be fixed.
 
     **It cost one golden case, exactly as predicted, and the cost turned out to be nothing.**
     The reference's `examples/strreverse.bas` names a variable `INPUT$`; the variable is renamed
-    to `SOURCE$` in `tests/reference/`, the expectation is byte-for-byte unchanged — the program
+    to `SOURCE$` in `tests/language/examples/strreverse.bas`, the expectation is byte-for-byte unchanged — the program
     still prints `REVERSED: OLLEH` — and the case keeps every bit of its coverage. Recorded in
-    `tests/reference/README.md`'s divergence table, which this is the first entry in.
+    `tests/language/README.md` records the corpus editing rule.
 
     This item sat parked because the corpus was the acceptance contract and lived in a submodule
     this repository could not edit. Both premises are gone: the corpus is checked in, and
@@ -2232,10 +2231,10 @@ update --init --recursive` gets them.
 
 ## 8. Status
 
-**The port is done.** The C interpreter passes the Go reference's entire corpus and passes clean
+**The port is done.** The C interpreter passes the language corpus and passes clean
 under ASan and UBSan. It reproduced that corpus byte for byte until §0.1 retired the
 requirement; two cases have diverged on purpose since, and
-`tests/reference/README.md` lists them.
+`tests/language/README.md` lists them.
 
 | Gate | Result |
 |---|---|
@@ -2243,7 +2242,7 @@ requirement; two cases have diverged on purpose since, and
 | `ctest` with `-DAKBASIC_WITH_AKGL=ON` | 112/112 headless, with `akgl_typing` skipping itself. The same set minus the four `no_device` cases the SDL driver contradicts, plus `akgl_backends`, `akgl_frontend`, `docs_screenshots` and `akgl_typing` — the last of which is the skip, and the `akgl_build` CI job is where it skips |
 | `docs_examples` | Every fenced block in `README.md`, `MAINTENANCE.md` and `docs/` executed and byte-compared: 71 programs, 9 transcripts, 79 output comparisons, 4 C snippets, 2 excerpts, 2 shell blocks and 19 figures in the default build. The C-snippet count reads 0 when the harness is run by hand without `--cflags-file`; CTest passes it. `MAINTENANCE.md` documents the fence-tag convention |
 | `docs_screenshots` | 19/19 figures re-rendered and byte-identical to the checked-in PNGs. AKGL build only — rendering a picture needs the SDL half |
-| Golden corpus | 41/41 byte-exact from `tests/reference/` — **and 41/41 again through the SDL binary**, which is most of what proves the frontend changes no output |
+| Language corpus | 65/65 paired expectations — **and 65/65 again through the SDL binary**, which is most of what proves the frontend changes no output |
 | ASan + UBSan | 112/112 |
 | Line coverage | 94.1% (7227/7681) — above the 90% gate |
 | Function coverage | 97.9% (474/484) |
@@ -2553,7 +2552,7 @@ What remains, in priority order:
       this whole arrangement exists against.
 
     The byte comparison is a deliberate bet that the dummy driver and the software renderer
-    are reproducible, which is the same bet `tests/reference/` already makes about golden
+    are reproducible, which is the same bet `tests/language/` makes about golden
     output. Verified run-to-run and build-to-build here; what is untested is an SDL upgrade
     that moves one pixel of a diagonal. **If that happens, regenerate the figures in the same
     commit as the bump** — do not weaken the test to a size check, which would pass for every
@@ -2636,7 +2635,7 @@ reduced against `build/basic`, the stdio build, unless it says otherwise.
 
    **It is narrower than it looks, and the golden corpus is why.** The first attempt
    released the scope on *any* skip, which broke
-   `tests/reference/language/flowcontrol/nestedforloopwaitingforcommand.bas`: a zero-
+   `tests/language/flowcontrol/nestedforloopwaitingforcommand.bas`: a zero-
    iteration `FOR` skips its body by the same mechanism, and there the orphan is
    load-bearing -- it is what absorbs the inner `NEXT` so the outer one still finds its
    `FOR`. Releasing it turns that case into "NEXT outside the context of FOR". So the

docs/14-architecture.md

@@ -743,8 +743,8 @@ way to see that something pushed a scope and never popped it.
 
 ```sh norun
 ctest --test-dir build --output-on-failure -R for_next     # one unit test
-ctest --test-dir build --output-on-failure -R golden_      # the reference corpus
-./build/basic tests/reference/language/functions.bas | diff - tests/reference/language/functions.txt
+ctest --test-dir build --output-on-failure -R local_       # the language corpus
+./build/basic tests/language/functions.bas | diff - tests/language/functions.txt
 ./tests/docs_examples.sh --root . --basic ./build/basic \
     --cflags-file build/docs_cflags.txt docs/14-architecture.md
 ```

scripts/mutation_test.py

@@ -282,9 +282,8 @@ def copy_tree(src, dst):
     # and a coverage tree drags along every .gcno/.gcda as well.
     #
     # deps/ is copied wholesale and has to be: the build pulls libakerror and
-    # libakstdlib in with add_subdirectory. The golden corpus used to be the
-    # other reason -- it was driven in place out of deps/basicinterpret -- and
-    # now lives in tests/reference/, which comes along with the rest of the tree.
+    # libakstdlib in with add_subdirectory. The language corpus is the other
+    # reason it comes along with the rest of the tree.
     # Only vendored Windows DLLs are dead weight, hence "*.dll".
     #
     # **PNGs are ours or theirs, and the difference matters.** This used to drop

src/runtime.c

@@ -893,7 +893,7 @@ akerr_ErrorContext *akbasic_runtime_interpret(akbasic_Runtime *obj, akbasic_ASTL
 	     *
 	     * **Only a block skip**, which is what the `BEND` test is for. A
 	     * zero-iteration `FOR` skips its body the same way, and there the
-	     * orphan is load-bearing: `tests/reference/.../nestedforloopwaiting
+	     * orphan is load-bearing: `tests/language/.../nestedforloopwaiting
 	     * forcommand.bas` nests a loop inside one that runs zero times, and
 	     * the inner scope is what absorbs the inner `NEXT` so the outer `NEXT`
 	     * still finds its `FOR`. Popping it there turns that case into "NEXT
@@ -1262,7 +1262,7 @@ akerr_ErrorContext *akbasic_runtime_process_line_runstream(akbasic_Runtime *obj)
      * This mode used to file it like any other, under the cursor -- which for a
      * blank line is the number of the line *before* it. A file ending in a blank
      * line therefore had its last line erased before it ever ran, silently. The
-     * reference did the same, and `tests/reference/language/arithmetic/integer.bas`
+     * reference did the same, and `tests/language/arithmetic/integer.bas`
      * has an expectation with three values for four PRINT statements to prove it.
      */
     if ( buffer[0] == '\0' ) {

tests/for_semantics.c

@@ -81,7 +81,7 @@ static void test_counter_survives_the_loop(void)
  * `FOR I = 1 TO 1` executes the body one time on every BASIC there has ever
  * been. Here the entry test treats "the counter has reached the limit" as
  * "do not enter", so the body is skipped entirely -- and
- * tests/reference/language/flowcontrol/forloopwaitingforcommand.bas pins that,
+ * tests/language/flowcontrol/forloopwaitingforcommand.bas pins that,
  * which is why this cannot simply be corrected.
  */
 static void test_single_iteration_loop(void)

tests/language/README.md

@@ -0,0 +1,16 @@
+# The language test corpus
+
+The `.bas` files in this directory and their sibling `.txt` files are the editable language
+corpus. CMake registers every program as an individual `local_*` CTest case and compares its
+output with the sibling expectation.
+
+The corpus includes cases carried over from the deprecated Go implementation as well as cases
+written for this interpreter. Their provenance is useful when investigating a regression, but it
+does not make any case immutable or turn the old implementation into a specification.
+
+**Change a program and its expectation deliberately and in the same commit.** If the changed
+output represents an intentional language decision, record the reason in `TODO.md` or the
+relevant documentation. If it is an accidental change, fix the interpreter instead.
+
+The `examples/` subdirectory contains complete BASIC programs used as worked examples. It is
+part of the same corpus and follows the same `.bas`/`.txt` pairing rule.

tests/reference/README.md

@@ -1,63 +0,0 @@
-# The reference interpreter's own test corpus
-
-These 41 `.bas` files and their 41 `.txt` expectations are **not this project's tests.** They
-are a byte-for-byte copy of the acceptance corpus belonging to the Go implementation this
-interpreter was ported from:
-
-| | |
-|---|---|
-| Source | `https://source.starfort.tech/andrew/basicinterpreter`, `tests/` |
-| Copied at | commit `d76162cb37eeaccddae2cf6cab7af7bc8175d6d2` ("Update README.md") |
-| Copied on | 2026-07-31 |
-| Verified | every file `cmp`-identical to the submodule at the time of the copy |
-
-They are registered as the `golden_*` CTest cases and run against `basic` on every build, in
-both the default and the `-DAKBASIC_WITH_AKGL=ON` configurations.
-
-## Why they are a copy, when they deliberately were not
-
-Until 2026-07-31 these were driven *in place* out of `deps/basicinterpret`, and the reasoning
-was written down in `CMakeLists.txt`: the corpus is a submodule, and copying a submodule's
-corpus guarantees drift.
-
-That reasoning was sound and it stopped applying. The Go project is deprecated and will not be
-updated, so there is nothing left to drift *from* — and a build that cannot run its own
-acceptance suite without cloning the implementation it replaced is not finished.
-
-## What these are for now
-
-**A regression suite, not a specification.** That distinction is the whole of how to treat
-them, and it changed on 2026-07-31 (`TODO.md` §0.1): matching the Go implementation is no
-longer a goal, so a difference between it and this interpreter is not automatically a bug in
-this one.
-
-What they are still good for is unchanged and is worth a lot: forty-one real BASIC programs
-with known-good output, covering arithmetic, arrays, flow control, every builtin function,
-`READ`/`DATA`, labels and three worked examples. That catches regressions whatever its
-provenance.
-
-## The rule for editing these
-
-**Diverge deliberately, never by accident.**
-
-A failure here means this interpreter's behaviour changed. Nine times in ten that is a bug you
-just introduced and the answer is to fix the code. The tenth time it is an improvement on the
-reference, and then the answer is:
-
-1. Change the expectation in the same commit as the code.
-2. Say why in the commit message.
-3. Add a line to `TODO.md` §5, which is the list of deliberate deviations.
-
-What is not acceptable is editing a `.txt` to make a red suite green without deciding which of
-the two you are doing.
-
-New cases for this project's own behaviour go in `tests/language/`, registered under `local_*`.
-The prefix says which corpus a failure came from, and a diff touching `tests/reference/` stands
-out as the thing it is.
-
-## Divergences so far
-
-| Case | Change | Why |
-|---|---|---|
-| `language/arithmetic/integer.txt` | Expectation grew from `4 4 2` to `4 4 2 2` | The program has **four** `PRINT` statements and the expectation had three values. The file ends in a blank line, and both interpreters filed a blank line under the loader's cursor — which for a line with no number of its own is the number of the line before it. So `40 PRINT 4 - 2` was erased before the program ran. The reference lost it the same way, which is why the expectation was written short. Fixed by skipping blank lines in RUNSTREAM, as `akbasic_runtime_load()` and `DLOAD` already did. `TODO.md` §5. |
-| `examples/strreverse.bas` | Variable `INPUT$` renamed to `SOURCE$` | `INPUT$` is a reserved word with a type suffix, which a real C128 refuses and which this interpreter now refuses too (`TODO.md` §6 item 16). The reference accepted it only because its own reserved-word check never fired. The expectation is byte-for-byte unchanged — the program still prints `REVERSED: OLLEH` — so the case keeps all of its value. |

tests/structure_verbs.c

@@ -358,7 +358,7 @@ static void test_skipped_block_releases_its_loop_scope(void)
  * inner `NEXT`, so the outer `NEXT` still finds its own `FOR`. Releasing it
  * turns this into "NEXT outside the context of FOR".
  *
- * tests/reference/language/flowcontrol/nestedforloopwaitingforcommand.bas is the
+ * tests/language/flowcontrol/nestedforloopwaitingforcommand.bas is the
  * golden case that caught exactly that, and this is the same shape asserted
  * where a reader of this file will see it.
  */

tests/unnumbered.c

@@ -182,7 +182,7 @@ static void test_runstream_assigns_the_same_slots(void)
 /**
  * @brief A file ending in a blank line keeps its last line.
  *
- * `tests/reference/language/arithmetic/integer.bas` is this shape, and both this
+ * `tests/language/arithmetic/integer.bas` is this shape, and both this
  * interpreter and the reference used to erase the last line before running it --
  * the blank line was filed under the cursor, which for a line with no number of
  * its own is the number of the line before it.