[!fuzz] skip
[short] skip

go test -fuzz=FuzzA -fuzztime=100x fuzz_setenv_test.go

-- fuzz_setenv_test.go --
package fuzz

import (
  "flag"
  "os"
  "testing"
)

func FuzzA(f *testing.F) {
  if s := os.Getenv("TEST_FUZZ_SETENV_A"); isWorker() && s == "" {
    f.Fatal("environment variable not set")
  } else if !isWorker() && s != "" {
    f.Fatal("environment variable already set")
  }
  f.Setenv("TEST_FUZZ_SETENV_A", "A")
  if os.Getenv("TEST_FUZZ_SETENV_A") == "" {
    f.Fatal("Setenv did not set environment variable")
  }
  f.Fuzz(func(*testing.T, []byte) {})
}

func FuzzB(f *testing.F) {
  if os.Getenv("TEST_FUZZ_SETENV_A") != "" {
    f.Fatal("environment variable not cleared after FuzzA")
  }
  f.Skip()
}

func isWorker() bool {
	f := flag.Lookup("test.fuzzworker")
	if f == nil {
		return false
	}
	get, ok := f.Value.(flag.Getter)
	if !ok {
		return false
	}
	return get.Get() == interface{}(true)
}