doc: tutorial for fuzz (using vscode)

[findleyr]

Add a tutorial document for writing Fuzz tests in VS Code.

CC @hyangah

[GlenDC]

Are you sure it even works? As it seems that a fuzz test only works when in the correct directory. For me when using run test on a fuzz test it even just does nothing. Just says "all ok". But it's the same as if you run go test -fuzz Fuzz in a directory containing no fuzz tests. From the CLI it does work where I go in the pkg dir and use the go test -fuzz Fuzz cmd.

[hyangah]

run test codelens invokes go test without -fuzz flag from the package's directory.
So, it doesn't fuzz.

[GlenDC]

So then what is #1794 all about? o.O

[hyangah]

#1794 made the extension to recognize the function named FuzzXXX.
If you have fuzz output, go test and so the run test codelens will run them.
Test explorer also recognizes the fuzz test data as subtests. This was
to support the case where - you find a crasher with go test -fuzz and
you fix the bug. When fixing the bug, you can utilize the run test codelens
or the test explorer UI to run and verify your fix actually addresses the problem.

About populating the fuzz data:

Fuzzing never ends by default so we don't know what's the UX users want.
If you have good ideas to integrate fuzzing in IDE, please share with us.
We are looking for ideas.

Meanwhile, users should run fuzz from terminal with go test -fuzz, or
you can define as one of the background task in tasks.json (we recently added
"go" type tasks, but you could achieve the same with the shell/process type
tasks too).

[krav-la]

Might be alright just to stop it manually probably how it's done in GoLand 'cause anyway it's how it's supposed to work, you run it, wait and stop as soon as you don't see any anomalies showing up right off the bat.