x/website/_content/doc/tutorial: go vet flags tutorial code for non-constant format string

[FelixDobler]

What is the URL of the page with the issue?

https://go.dev/doc/tutorial/add-a-test

What is your user agent?

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:138.0) Gecko/20100101 Firefox/138.0

Screenshot

What did you do?

Follow the steps in the tutorial.

What did you expect to see?

I expected to see the same command output for go test in the tutorial as on my local machine when executing the command.

What did you see instead?

For step 5, the outputs don't match. It seems like go now does advanced code checking and already detects a static issue without running the actual test.

Tutorial Output

$ go test
--- FAIL: TestHelloName (0.00s)
    greetings_test.go:15: Hello("Gladys") = "Hail, %v! Well met!", <nil>, want match for `\bGladys\b`, nil
FAIL
exit status 1
FAIL    example.com/greetings   0.182s

Local Output

using go version go1.24.2 windows/amd64

$ go test
# exammple.com/greetings
# [exammple.com/greetings]
.\greetings.go:20:25: non-constant format string in call to fmt.Sprintf
FAIL    exammple.com/greetings [build failed]

[FelixDobler]

If desired, I can create a PR that circumvents the changed test behavior by e.g. replacing the name to be used in the formatted string with a static one.

[gabyhelp]

Related Issues

• testing: show diffs for incorrect output from Example tests #41980
• x/website: #51742 (closed)
• x/tools/analysis/passes/tests: report examples with misplaced Output comments #48362 (closed)
• x/website: error and suggestion for tutorials pages #41150 (closed)
• x/website: #60987 (closed)
• x/website: #61392 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[adonovan]

Thanks for the bug report. I read through the tutorial but was unable to see any mistake that would cause that error. Can you include the exact contents of the files at the moment you observed the error? I wonder whether you have a stray backquote, for example fmt.Sprintf(`pattern, arg`) instead of fmt.Sprintf(`pattern`, arg) .

[FelixDobler]

Oh you're right, in step 4 of the "create a test" tutorial it replaces
message := fmt.Sprintf(randomFormat(), name)
with
message := fmt.Sprint(randomFormat())
removing the f from Sprintf and hence changing the function signature.

Sorry for binding resources with such a simple oversight.
Cheers!