Re: [PATCH v7 02/10] test-lib-functions: improve diagnostic output for trace2 data assertions

>
> From: Kristofer Karlsson <krka@spotify.com>
>
> test_trace2_data is a bare grep that silently exits on failure.
> Add a more informative variant that verifies the event appears
> exactly once and reports what went wrong: key not found, multiple
> entries, or value mismatch. Diagnostics go to FD 4 like test_grep.
>
> Before (value mismatch):
>
>   $ test_trace2_data status count/changed 999 <trace2.txt
>   $ echo $?
>   1
>   (no output)
>
> After:
>
>   $ test_trace2_data_singular status count/changed 999 <trace2.txt
>   error: trace2 data 'status/count/changed'
>     expected: 999
>     actual:   0

> Signed-off-by: Kristofer Karlsson <krka@spotify.com>
> ---
>  t/test-lib-functions.sh | 35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
>
> diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
> index 809c662124..8c6d327b03 100644
> --- a/t/test-lib-functions.sh
> +++ b/t/test-lib-functions.sh
> @@ -1996,6 +1996,41 @@ test_trace2_data () {
>         grep -e '"category":"'"$1"'","key":"'"$2"'","value":"'"$3"'"'
>  }
>
> +# Check that the given trace2 data event has the expected value and
> +# appears exactly once.  Produces a diagnostic on failure.
> +#
> +#      test_trace2_data_singular <category> <key> <value> [<label>]
> +test_trace2_data_singular () {
> +       local category="$1" key="$2" expect_val="$3"
> +       local label_suffix="${4:+ [$4]}"
> +       local kv_pattern='"category":"'"$category"'","key":"'"$key"'","value":"\([^"]*\)"'
> +       local actual
> +
> +       actual=$(sed -n "s|.*${kv_pattern}.*|\1|p") &&
> +
> +       if test -z "$actual"
> +       then
> +               echo >&4 "error: trace2 data '$category/$key'$label_suffix not found"
> +               return 1
> +       fi &&
> +
> +       case "$actual" in
> +       *"$LF"*)

> +               echo >&4 "error: trace2 data '$category/$key'$label_suffix has multiple entries, expected 1"
> +               printf '%s\n' "$actual" | sed 's/^/  actual:   /' >&4
> +               return 1
> +               ;;
> +       esac &&
> +
> +       if test "$actual" != "$expect_val"
> +       then
> +               echo >&4 "error: trace2 data '$category/$key'$label_suffix"
> +               echo >&4 "  expected: $expect_val"
> +               echo >&4 "  actual:   $actual"
> +               return 1
> +       fi
> +}
> +