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:

Change the expectation in the same commit as the code.
Say why in the commit message.
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.