mutastic next

Show the missed mutant most worth a test first, and why. The missed mutants as a queue, one line's at a time, in the order a run ranks them: its card, why it's first, and the command that says when it's done. --top shows the first few, spread over the code. With a baseline, new misses come before the baseline's. While the code under test is the same, it runs only the mutants the last next left uncaught, so any a new test catches drop out; once that code changes, it runs every mutant again. A mutant proposed for ignoring isn't queued: it waits on a person. For an agent, one task, and to run next again after it.

Usage

mutastic next [dir] [options]

Inside a package, cargo mutastic next runs the same command, with the same options.

mutastic next
mutastic next --top=5
mutastic next --format=agent

Output

This is mutastic's own output, written from the CLI and checked against it on every build.

Next: 1 of 3 lines with missed mutants in ranking

  ✗ MISSED  no test checks is_small() at n == 10 · md0d6db64
    ┌─ src/lib.rs:15
    │
 14 │ pub fn is_small(n: u32) -> bool {
 15 │     n < 10
    │       ^ < changed to <=
 16 │ }
    │
    = mutant  - n < 10
              + n <= 10
    = also    ✗ no test checks is_small() returning false here · m2e329a72
              + true
    = also    ✗ no test needs n < 10 to be false in is_small() · m729a5380
              + true
    = note: every test calls is_small() away from the boundary
            inputs seen: 4, 5, 6 (none is 10)
            covered by tests::five_doubled_is_more_than_one_and_small, tests::four_doubled_is_more_than_one_and_small, tests::six_doubled_is_more_than_one_and_small (all 3 covering tests still pass)
    = help: test is_small() with n = 10 and assert the result

            // in mod tests
            #[test]
            fn is_small_at_the_n_edge() {
                assert!(!is_small(10)); // today false · with md0d6db64 true
            }
            check today's value is the one you intend: the test pins what the code does now

    done when  mutastic verify md0d6db64,m2e329a72,m729a5380 fixtures/ranking passes
    reproduce  mutastic run --only=md0d6db64,m2e329a72,m729a5380 fixtures/ranking
    or ignore  mutastic ignore <id> --reason="<why>" fixtures/ranking for each of md0d6db64, m2e329a72, m729a5380
 Ranked first because
   a condition or a removal: it changes what the code decides or does
   3 tests run it, and none checks it

Then: mutastic next fixtures/ranking, for the next one

Exit status

0 when nothing missed is left, or only mutants proposed for ignoring; 1 while something is queued. Any command exits 2 when mutastic couldn't run: see exit codes.

Options

--since[=REF]

Mutate only the lines changed since the merge-base of HEAD and REF, uncommitted and new files included; the default branch without one.

Command line	--since[=REF]

mutastic next --since=main

--workers=N

How many mutants run side by side; half the cores, from 1 to 4, unless set.

Command line	--workers=N

mutastic next --workers=2

--no-suggestions

Don't look for a test that catches each missed mutant, which runs the missed mutant's function outside the tests.

Command line	--no-suggestions

mutastic next --no-suggestions

--operators=OPERATORS

Which operators run: a set (defaults, stronger or extended), or operator ids split by commas, in place of mutastic.yaml's operators; defaults unless set.

Command line	--operators=OPERATORS

mutastic next --operators=stronger

--unsafe=MODE

Which unsafe code is mutated: skip leaves unsafe code and the functions holding an unsafe block alone, enclosing mutates those functions too, all unsafe code as well; skip unless set.

One of skipenclosingall

Command line	--unsafe=MODE

mutastic next --unsafe=enclosing

--format=FORMAT

How the result is shown; full on a terminal, concise elsewhere, agent for coding agents; explain takes full and jsonl.

One of fullbriefconcisegroupedagentjsonl

Command line	--format=FORMAT
Environment	MUTASTIC_FORMAT, MUTASTIC_AGENT

mutastic next --format=jsonl

--vocabulary=WORDS

plain says caught and missed; classic says killed and survived.

One of plainclassic

Command line	--vocabulary=WORDS
Environment	MUTASTIC_VOCABULARY

mutastic next --vocabulary=classic

--color=WHEN

Colour: auto uses it on a terminal that wants it.

One of autoalwaysnever

Command line	--color=WHEN
Environment	NO_COLOR, FORCE_COLOR

mutastic next --color=never

--hyperlinks=WHEN

File locations as links a terminal can open: auto uses them on a terminal.

One of autoalwaysnever

Command line	--hyperlinks=WHEN

mutastic next --hyperlinks=never

--progress=STYLE

Progress on stderr: a bar on a terminal, counter lines in logs, none for agents.

One of autobarcounternone

Command line	--progress=STYLE

mutastic next --progress=counter

--top=N

How many of the queue next shows, at most one a function and two a file; 1 unless set, at most 25.

Command line	--top=N

mutastic next --top=5

--edition=EDITION

Which edition runs; unless set, the build file in dir, or the nearest above it: Cargo.toml for rust, pom.xml, build.gradle or settings.gradle for java.

One of rustjava

Command line	--edition=EDITION

mutastic next --edition=rust