mutator

Overview ¶

Package mutator defines the Mutator function type and the registration mechanism used by all built-in and third-party mutation operators.

Implementing a custom operator requires three steps:

1. Write a function with the Mutator signature.
2. Call Register from an init() function so it is available at startup.
3. Import your package (blank import) in a fork of cmd/go-mutesting/main.go.

Example:

func init() {
    mutator.Register("mypkg/flip-sign", flipSign)
}

func flipSign(_ *types.Package, _ *types.Info, node ast.Node) []mutator.Mutation {
    n, ok := node.(*ast.UnaryExpr)
    if !ok || n.Op != token.SUB {
        return nil
    }
    return []mutator.Mutation{
        {Change: func() { n.Op = token.ADD }, Reset: func() { n.Op = token.SUB }},
    }
}