Add mutation testing to validate the test suite
Introduce a self-contained mutation testing harness that verifies the unit
tests actually catch bugs: it makes small deliberate breakages to the library
(flip comparisons, delete statements, swap true/false, etc.), rebuilds, and
runs the whole CTest suite against each mutant. Tests that still pass reveal a
gap; tests that fail "kill" the mutant.
- scripts/mutation_test.py: the engine (stdlib only, no LLVM/clang deps).
Operators ROR/LCR/BCR/AOR/ICR/SDL over src/error.c and the macro header.
Mutates a scratch copy, never the working tree. Supports --target, --list,
--max-mutants sampling, --threshold gating, --timeout.
- CMakeLists.txt: 'mutation' custom target (cmake --build build --target mutation).
- .gitea/workflows/ci.yaml: gated mutation job on src/error.c (threshold 65%).
- tests/MUTATION.md: how to run, interpret survivors, and known equivalents.
Close the real gaps the harness found in src/error.c (score 53% -> 71%):
- err_error_names: the AKERR_* codes have their names registered by akerr_init
- err_release_clears: releasing a context wipes it before reuse
- err_pool_exhaust: akerr_next_error returns NULL when the pool is full and
always hands back the lowest free slot
Also surfaced (documented, not fixed): AKERR_MAX_ERR_VALUE (+15) is below
AKERR_NOT_IMPLEMENTED (+16) and AKERR_BADEXC (+17), so those codes can never
have a name registered.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-07-27 17:03:53 -04:00
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#include "akerror.h"
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#include "err_capture.h"
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#include <string.h>
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/*
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* Releasing an error context back to the pool must wipe it, so the next caller
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* that checks it out never sees stale status/message/stacktrace from a previous
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* error. Mutation testing showed the clearing memset in akerr_release_error
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* could be deleted without any test noticing.
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*/
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akerr_ErrorContext *boom(void)
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{
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PREPARE_ERROR(e);
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FAIL_RETURN(e, AKERR_VALUE, "stale dirty message that must not survive");
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}
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int main(void)
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{
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akerr_capture_install();
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akerr_init();
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/* Raise and fully handle an error; FINISH_NORETURN releases it to the pool. */
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PREPARE_ERROR(e);
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ATTEMPT {
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CATCH(e, boom());
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} CLEANUP {
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} PROCESS(e) {
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} HANDLE(e, AKERR_VALUE) {
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2026-07-29 17:09:45 -04:00
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AKERR_CHECK_STATUS(e, AKERR_VALUE);
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Add mutation testing to validate the test suite
Introduce a self-contained mutation testing harness that verifies the unit
tests actually catch bugs: it makes small deliberate breakages to the library
(flip comparisons, delete statements, swap true/false, etc.), rebuilds, and
runs the whole CTest suite against each mutant. Tests that still pass reveal a
gap; tests that fail "kill" the mutant.
- scripts/mutation_test.py: the engine (stdlib only, no LLVM/clang deps).
Operators ROR/LCR/BCR/AOR/ICR/SDL over src/error.c and the macro header.
Mutates a scratch copy, never the working tree. Supports --target, --list,
--max-mutants sampling, --threshold gating, --timeout.
- CMakeLists.txt: 'mutation' custom target (cmake --build build --target mutation).
- .gitea/workflows/ci.yaml: gated mutation job on src/error.c (threshold 65%).
- tests/MUTATION.md: how to run, interpret survivors, and known equivalents.
Close the real gaps the harness found in src/error.c (score 53% -> 71%):
- err_error_names: the AKERR_* codes have their names registered by akerr_init
- err_release_clears: releasing a context wipes it before reuse
- err_pool_exhaust: akerr_next_error returns NULL when the pool is full and
always hands back the lowest free slot
Also surfaced (documented, not fixed): AKERR_MAX_ERR_VALUE (+15) is below
AKERR_NOT_IMPLEMENTED (+16) and AKERR_BADEXC (+17), so those codes can never
have a name registered.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-07-27 17:03:53 -04:00
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} FINISH_NORETURN(e);
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AKERR_CHECK(e == NULL);
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/* The next context handed out is the slot we just released: it must be clean. */
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akerr_ErrorContext *slot = akerr_next_error();
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AKERR_CHECK(slot != NULL);
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AKERR_CHECK(slot->status == 0);
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AKERR_CHECK(slot->message[0] == '\0');
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AKERR_CHECK(slot->stacktracebuf[0] == '\0');
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AKERR_CHECK(strstr(slot->message, "stale dirty message") == NULL);
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fprintf(stderr, "err_release_clears ok\n");
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return 0;
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}
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