groxx / gofuzz

Fuzz testing for go.

Planned changes so I don't forget

• generating into anything which (transitively) includes an interface panics. that's kinda crazy, make that optional.
• add a private-type-compatible fuzz-func registry so things like proto OneOf fields (the field type is a private interface) can be detected, and a valid value returned (e.g. a publicly-exposed enum).

gofuzz

gofuzz is a library for populating go objects with random values.

This is useful for testing:

• Do your project's objects really serialize/unserialize correctly in all cases?
• Is there an incorrectly formatted object that will cause your project to panic?

Import with import "github.com/google/gofuzz"

You can use it on single variables:

f := fuzz.New()
var myInt int
f.Fuzz(&myInt) // myInt gets a random value.

You can use it on maps:

f := fuzz.New().NilChance(0).NumElements(1, 1)
var myMap map[ComplexKeyType]string
f.Fuzz(&myMap) // myMap will have exactly one element.

Customize the chance of getting a nil pointer:

f := fuzz.New().NilChance(.5)
var fancyStruct struct {
  A, B, C, D *string
}
f.Fuzz(&fancyStruct) // About half the pointers should be set.

You can even customize the randomization completely if needed:

type MyEnum string
const (
        A MyEnum = "A"
        B MyEnum = "B"
)
type MyInfo struct {
        Type MyEnum
        AInfo *string
        BInfo *string
}

f := fuzz.New().NilChance(0).Funcs(
        func(e *MyInfo, c fuzz.Continue) {
                switch c.Intn(2) {
                case 0:
                        e.Type = A
                        c.Fuzz(&e.AInfo)
                case 1:
                        e.Type = B
                        c.Fuzz(&e.BInfo)
                }
        },
)

var myObject MyInfo
f.Fuzz(&myObject) // Type will correspond to whether A or B info is set.

See more examples in example_test.go.

dvyukov/go-fuzz integration

You can use this library for easier go-fuzzing. go-fuzz provides the user a byte-slice, which should be converted to different inputs for the tested function. This library can help convert the byte slice. Consider for example a fuzz test for a the function mypackage.MyFunc that takes an int arguments:

// +build gofuzz
package mypackage

import fuzz "github.com/google/gofuzz"

func Fuzz(data []byte) int {
        var i int
        fuzz.NewFromGoFuzz(data).Fuzz(&i)
        MyFunc(i)
        return 0
}

Happy testing!