selene

README

selene

Selene is a mutation testing tool for Go. It helps you verify the quality of your test suite by ensuring that your tests fail when the code is modified (mutated).

How it works

The tool reads the source files, parses the AST, replaces relevant nodes (mutations), and writes the modified source to a temporary folder. Then, it runs go test using the -overlay flag to replace the original files with the mutated ones during compilation.

Supported Mutators

• ReverseIfCond: Reverses boolean expressions in if statements (e.g., if x > 0 becomes if !(x > 0)).
• SwapArithmetic: Swaps arithmetic operators (e.g., + becomes -, * becomes /).

Installation

Install directly using go install:

go install github.com/danicat/selene@latest

Or build from source:

go build -o selene .

Usage

Run mutation testing on specific files or package patterns:

# Run on specific files
./selene run <file1.go> <file2.go> ...

# Run on all files in the current package and subpackages
./selene run ./...

Example

$ ./selene run ./...
Mutation directory: /var/folders/.../T/mutation12345
Running tests to generate coverage profile...
ReverseIfCond-internal/mutator/mutator.go:50:8: killed
SwapArithmetic-internal/mutator/swap_arithmetic.go:19:52: killed
Comparison-internal/mutator/comparison.go:10:15: uncovered

Total mutations: 3
Killed:          2
Survived:        0
Uncovered:       1
Mutation Score:  100.00% (killed/covered)

Options

Flag	Description
--mutation-dir	Directory to store mutations (default: temporary directory).
--mutators	Comma-separated list of mutators to enable (e.g., ReverseIfCond,SwapArithmetic). If empty, all mutators are enabled by default.

Selene automatically runs go test to generate a coverage profile and skips mutations on uncovered code.

# Run with specific mutators
./selene run --mutators=SwapArithmetic testdata/arithmetic.go

Why Selene?

Selene is the oldest known human mutant in Marvel comics. It's also the name of the best protagonist of a vampire movie ever.