NEWS

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muttest 0.3.0 (2026-07-21)

• ✨ New JSONMutationReporter writes a report conforming to the mutation-testing-elements schema, a cross-language standard shared by StrykerJS/.NET/Scala — so muttest output can be fed to any schema-compatible tooling.
• ✨ New report() renders a self-contained, source-annotated HTML report (overall score, per-file breakdown, per-line mutant diffs, status filtering, keyboard navigation) from a JSONMutationReporter file.
• ✨ New MultiReporter fans reporter events out to several reporters at once, e.g. a live ProgressMutationReporter alongside a JSONMutationReporter.
• ❗️ A mutant that makes tests error (rather than fail an expectation) is now scored as killed, matching PIT/Stryker/mutmut. Previously it was counted as survived.
• ❗️ Mutants with no test coverage (no matching test file under FileTestStrategy) are now reported as a separate no coverage category and excluded from the score, so untested code no longer looks like escaped mutants.
• ✨ PackageCopyStrategy gained a symlink argument. When TRUE, only the mutated file's top-level directory is copied and everything else is symlinked to the original, avoiding a full project copy per mutant (helpful for packages with large inst//data/). Defaults to FALSE; unsafe if the test suite writes into the package's own directories.
• 🐛 FileTestStrategy now matches test files by exact name instead of an unanchored regex, so a source file like mod.R no longer runs test-model.R and filenames with regex metacharacters are handled correctly.
• 🐛 Added missing digest and tools to Imports.

muttest 0.2.1 (2026-06-24)

• Update treesitter queries to work with treesitter >= 1.3.0.

muttest 0.2.0 (2026-05-14)

• ❗️ Renamed plan() to muttest_plan().
• ✨ Add new mutators:
  • boolean_literal(), na_literal() — literal replacement mutators.
  • negate_condition(), remove_condition_negation() — condition mutators.
  • numeric_increment(), numeric_decrement(), index_increment(), index_decrement() — increment/decrement mutators.
  • string_empty(), string_fill() — string mutators.
  • call_name() — call name mutator.
  • remove_negation() — unary negation mutator.
  • replace_return_value() — return value mutator.
  • delete_statement() — removes assignments and standalone calls one at a time to catch untested side effects and dead assignments.
• ✨ Add preset collections for all major mutator groups:
  • boolean_literals() — flips TRUE/FALSE and T/F.
  • na_literals() — swaps NA, NULL, and typed NA variants.
  • numeric_literals() — increments and decrements numeric constants.
  • index_mutations() — shifts subscript indices up and down by one.
  • string_literals() — empties non-empty strings and fills empty ones.
  • condition_mutations() — negates conditions and removes existing negations.
  • arithmetic_operators() — mutates arithmetic operators (+, -, *, /, ^, %%, %/%).
  • comparison_operators() — mutates comparison operators (<, >, <=, >=, ==, !=).
  • logical_operators() — mutates logical operators (&, |, &&, ||).
• ✨ Mutators are now parametrized and accept configuration arguments.
• ✨ ProgressMutationReporter now reports survived mutants.
• ✨ Expose Mutator base class for building custom mutators.
• ✨ muttest() supports parallel execution of mutants.
• ✨ muttest() supports per-mutant timeouts to avoid hanging test runs.
• 🥅 Improved error handling when test execution fails.

muttest 0.1.0 (2025-05-30)

• ✨ Create a testing plan with plan.
• ✨ Run mutation testing with muttest.
• ✨ Support mutating operators with operator.
• ✨ Control copying project to temporary directory with CopyStrategy:
  • PackageCopyStrategy implemented for copying package files.
• ✨ Control test execution for each mutant with TestStrategy:
  • FullTestStrategy for running all tests for each mutant.
  • FileTestStrategy for running only test files matching mutant files.
• ✨ See test results with MutationReporter.
  • ProgressMutationReporter for printing progress to the console.