proposal: testing: export test/benchmark name

[RaduBerinde]

This is a proposal to add a Name() string function to testing.TB that returns the name of the test/benchmark. This is necessary to differentiate between debugging messages, events, traces etc when running tests/benchmarks in parallel.

In many cases one can figure out the enclosing Test.. function by studying the caller stack but that wouldn't work for subtests. This feature would be especially useful when the subtests are generated programatically, e.g. for i := 1; i <= 5; i++ { t.Run(fmt.Sprintf("i=%d", i), ..)

[josharian]

Interesting. Somewhat related: #4899. cc @adg @mpvl @robpike

[quentinmit]

I feel like this is solving the wrong problem; the TB already knows which subtest it is for, maybe the log output should just be changed to prepend every log message with the name of the test?

Also the hypothetical JSON output (#2981) separates log messages by test.

[RaduBerinde]

That is only helpful for logs that go through TB. Tests might spin up non-testing machinery which can have its own internal methods for outputting debug messages. Plus this is not limited to printed logs, it could be used for other things like traces (e.g. LightStep).

[adg]

Fixed in #17231.