src/cmd/go/testdata/script/test_fuzz_fuzztime.txt

[!fuzz] skip
[short] skip
env GOCACHE=$WORK/cache

# There are no seed values, so 'go test' should finish quickly.
go test

# For the fuzzing phase, we reduce GOMAXPROCS to avoid consuming too many
# resources during the test. Ideally this would just free up resources to run
# other parallel tests more quickly, but unfortunately it is actually necessary
# in some 32-bit environments to prevent the fuzzing engine from running out of
# address space (see https://go.dev/issue/65434).
env GOMAXPROCS=2

# Fuzzing should exit 0 after fuzztime, even if timeout is short.
go test -timeout=3s -fuzz=FuzzFast -fuzztime=5s

# We should see the same behavior when invoking the test binary directly.
go test -c
exec ./fuzz.test$GOEXE -test.timeout=3s -test.fuzz=FuzzFast -test.fuzztime=5s -test.parallel=1 -test.fuzzcachedir=$WORK/cache

# Timeout should not cause inputs to be written as crashers.
! exists testdata/fuzz

# When we use fuzztime with an "x" suffix, it runs a specific number of times.
# This fuzz function creates a file with a unique name ($pid.$count) on each
# run. We count the files to find the number of runs.
mkdir count
go test -fuzz=FuzzTestCount -fuzztime=1000x -fuzzminimizetime=1x
go run check_file_count.go count 1000

# When we use fuzzminimizetime with an "x" suffix, it runs a specific number of
# times while minimizing. This fuzz function creates a file with a unique name
# ($pid.$count) on each run once the first crash has been found. That means that
# there should be one file for each execution of the fuzz function during
# minimization, so we count these to determine how many times minimization was
# run.
mkdir minimizecount
! go test -fuzz=FuzzMinimizeCount -fuzzminimizetime=3x -parallel=1
go run check_file_count.go minimizecount 3

-- go.mod --
module fuzz

go 1.16
-- fuzz_fast_test.go --
package fuzz_test

import "testing"

func FuzzFast(f *testing.F) {
	f.Fuzz(func (*testing.T, []byte) {})
}
-- fuzz_count_test.go --
package fuzz

import (
	"fmt"
	"os"
	"testing"
)

func FuzzTestCount(f *testing.F) {
	pid := os.Getpid()
	n := 0
	f.Fuzz(func(t *testing.T, _ []byte) {
		name := fmt.Sprintf("count/%v.%d", pid, n)
		if err := os.WriteFile(name, nil, 0666); err != nil {
			t.Fatal(err)
		}
		n++
	})
}
-- fuzz_minimize_count_test.go --
package fuzz

import (
	"bytes"
	"fmt"
	"os"
	"testing"
)

func FuzzMinimizeCount(f *testing.F) {
	pid := os.Getpid()
	n := 0
	seed := bytes.Repeat([]byte("a"), 357)
	f.Add(seed)
	crashFound := false
	f.Fuzz(func(t *testing.T, b []byte) {
		if crashFound {
			name := fmt.Sprintf("minimizecount/%v.%d", pid, n)
			if err := os.WriteFile(name, nil, 0666); err != nil {
				t.Fatal(err)
			}
			n++
		}
		if !bytes.Equal(b, seed) {  // this should happen right away
			crashFound = true
			t.Error("minimize this!")
		}
	})
}
-- check_file_count.go --
// +build ignore

package main

import (
	"fmt"
	"os"
	"strconv"
)

func main() {
	dir, err := os.ReadDir(os.Args[1])
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	got := len(dir)
	want, _ := strconv.Atoi(os.Args[2])
	if got != want {
		fmt.Fprintf(os.Stderr, "got %d files; want %d\n", got, want)
		os.Exit(1)
	}
}