-h is not a valid flag for go help, so go test -h writes usage to stderr, not stdout, and exits with a non-zero exit code. The pipe only sends stdout to less.

The correct command to view help for go test is via the go help command:

go help test

Since it's a valid command, it prints to stdout and exits with zero exit code. So, you can do what you want:

go help test | less

As far as I know, this behavior is consistent with Unix-y tools.

E.g., git help writes help to stdout and exists with zero code. git -help writes "unknown option: -help" and usage to stderr and exists with non-zero code.

If you wanted to read go test -h output with less, despite it not being a valid flag, you can just redirect stderr to stdout before piping to less:

go test -h 2>&1 | less

I don't think -h is an invalid flag. I'm using go build here to demonstrate because go test -h is massive (that's #26999):

$ go build -h
usage: go build [-o output] [-i] [build flags] [packages]
Run 'go help build' for details.
$ go build -asdf
flag provided but not defined: -asdf
usage: go build [-o output] [-i] [build flags] [packages]
Run 'go help build' for details.

However, I agree that it's normal for usage text to be printed to stderr. A shorter version of what Dmitri suggested above, if you're on Bash, is go test -h |& less.

The issue I linked above would also fix your issue, I believe. go test -h should not output pages of text.

Thanks for the correction @mvdan, -h is indeed a valid flag.

I see what you guys are saying. go test -h should behave like go build -h anyway. My issue was more that the behavior seemed to have changed, but I'll just use go help in the future, so it's not an issue.