_content/fuzz-beta.article: add article for fuzz beta
Change-Id: I10fb5478db02d5a122db910c6f516a51c62e80b6
Reviewed-on: https://go-review.googlesource.com/c/website/+/324789
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
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+# Fuzzing is Beta Ready
+03 Jun 2021
+Tags: fuzz, testing
+Summary: Native Go fuzzing is now ready for beta testing in the dev.fuzz development branch.
+
+Katie Hockman
+
+Jay Conrod
+
+##
+
+We are excited to announce that native fuzzing is ready for beta testing in its
+development branch, [dev.fuzz](https://github.com/golang/go/tree/dev.fuzz)!
+
+Fuzzing is a type of automated testing which continuously manipulates inputs to
+a program to find issues such as panics or bugs. These semi-random data
+mutations can discover new code coverage that existing unit tests may miss, and
+uncover edge case bugs which would otherwise go unnoticed. Since fuzzing can
+reach these edge cases, fuzz testing is particularly valuable for finding
+security exploits and vulnerabilities.
+
+See
+[golang.org/s/draft-fuzzing-design](https://golang.org/s/draft-fuzzing-design)
+for more details about this feature.
+
+
+## Getting started
+
+To get started, you may run the following
+
+ $ go get golang.org/dl/gotip
+ $ gotip download dev.fuzz
+
+This builds the Go toolchain from the dev.fuzz development branch, and won’t be
+needed once the code is merged to the master branch in the future. After running
+this, `gotip` can act as a drop-in replacement for the `go` command. You can now
+run commands like
+
+ $ gotip test -fuzz=FuzzFoo
+
+There will be ongoing development and bug fixes in the dev.fuzz branch, so you
+should regularly run `gotip download dev.fuzz` to use the latest code.
+
+For compatibility with released versions of Go, use the gofuzzbeta build tag
+when committing source files containing fuzz targets to your repository. This
+tag is enabled by default at build-time in the dev.fuzz branch. See the [go
+command documentation about build
+tags](https://golang.org/cmd/go/#hdr-Build_constraints) if you have questions
+about how to use them.
+
+ // +build gofuzzbeta
+
+## Writing a fuzz target
+
+A fuzz target must be in a \*\_test.go file as a function in the form `FuzzXxx`.
+This function must be passed a` *testing.F` argument, much like a `*testing.T`
+argument is passed to a `TestXxx` function.
+
+Below is an example of a fuzz target that’s testing the behavior of the [net/url
+package](https://pkg.go.dev/net/url#ParseQuery).
+
+ // +build gofuzzbeta
+
+ package fuzz
+
+ import (
+ "net/url"
+ "reflect"
+ "testing"
+ )
+
+ func FuzzParseQuery(f *testing.F) {
+ f.Add("x=1&y=2")
+ f.Fuzz(func(t *testing.T, queryStr string) {
+ query, err := url.ParseQuery(queryStr)
+ if err != nil {
+ t.Skip()
+ }
+ queryStr2 := query.Encode()
+ query2, err := url.ParseQuery(queryStr2)
+ if err != nil {
+ t.Fatalf("ParseQuery failed to decode a valid encoded query %s: %v", queryStr2, err)
+ }
+ if !reflect.DeepEqual(query, query2) {
+ t.Errorf("ParseQuery gave different query after being encoded\nbefore: %v\nafter: %v", query, query2)
+ }
+ })
+ }
+
+You can read more about the fuzzing APIs with go doc
+
+ gotip doc testing
+ gotip doc testing.F
+ gotip doc testing.F.Add
+ gotip doc testing.F.Fuzz
+
+## Expectations
+
+This is a beta release in a development branch, so you should expect some bugs
+and an incomplete feature set. Check the [issue tracker for issues labelled
+“fuzz”](https://github.com/golang/go/issues?q=is%3Aopen+is%3Aissue+label%3Afuzz)
+to stay up-to-date on existing bugs and missing features.
+
+Please be aware that fuzzing can consume a lot of memory and may impact your
+machine’s performance while it runs. `go test -fuzz` defaults to running fuzzing
+in `$GOMAXPROCS` processes in parallel. You may lower the number of processes
+used while fuzzing by explicitly setting the `-parallel` flag with `go test`.
+Read the documentation for the `go test` command by running `gotip help
+testflag` if you want more information.
+
+Also be aware that the fuzzing engine writes values that expand test coverage to
+a fuzz cache directory within `$GOCACHE/fuzz` while it runs. There is currently
+no limit to the number of files or total bytes that may be written to the fuzz
+cache, so it may occupy a large amount of storage (ie. several GBs). You can
+clear the fuzz cache by running `gotip clean -fuzzcache`.
+
+## What’s next?
+
+This feature will not be available in the upcoming Go release (1.17), but there
+are plans to land this in a future Go release. We hope that this working
+prototype will allow Go developers to start writing fuzz targets and provide
+helpful feedback about the design in preparation for a merge to master.
+
+If you experience any problems or have an idea for a feature request, please
+[file an
+issue](https://github.com/golang/go/issues/new/?&labels=fuzz&title=%5Bdev%2Efuzz%5D&milestone=backlog&body=).
+
+For discussion and general feedback about the feature, you can also participate
+in the [#fuzzing channel](https://gophers.slack.com/archives/CH5KV1AKE) in
+Gophers Slack.
+
+Happy fuzzing!
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