How do I fuzz a nil value in Go 1.18?

I am trying to use Go 1.18 go test -fuzz command to fuzz nil values so that I can ensure I didn't forget safety checks before attempting to dereference a pointer to a string.

Here is my attempt:

// main.go
package main

import (
	"fmt"
)

func HandleString(s *string) {
	// most common programmer error is dereferencing nil pointers without safety checks
	fmt.Println(*s)
}

func main() {
	s := "Hello, world"
	HandleString(&s)
}

// main_test.go
package main

import "testing"

func FuzzHandleString(f *testing.F) {
	h := "hello world"
	for _, seed := range []*string{nil, new(string), &h} {
		f.Add(seed)
	}
	f.Fuzz(func(t *testing.T, in *string) {
		HandleString(in)
	})
}

Unfortunately i get an error saying go fuzz doesn't support pointers and only supports the string datatype.

I found a workaround by writing my test like this:

package main

import "testing"

func FuzzHandleString(f *testing.F) {
	h := "hello world"
	for _, seed := range []string{"-1", "", h} {
		f.Add(seed)
	}
	f.Fuzz(func(t *testing.T, in string) {
		if in == "-1" {
			HandleString(nil)
		} else {
			HandleString(&in)
		}
	})
}

This is a horrible design, and makes the seed data array not easily reusable , and requires logic in every fuzz function to trick my method into taking a nil value.

Surely there has to be a better way I didn't think of?

Thanks

Your code is awkward because this is not what fuzzing is for. Fuzzing is to throw random values at your functions to test edge cases you may not have thought about.

What you're doing is more like bounds testing. You have a known tricky inputs like nil, or empty string, or an empty array. Test them in their own unit tests.

Finally, I'd question why nil is a valid input to handleString. nil is not a string. It should be an error, unless there's a good reason otherwise, and you should be testing for that error.