way of silencing 'this run has ID <…>' ?

[c-cube]

I'm trying to turn a (failing) alcotest binary into a dune expect test, but it's unreproducible because of one line: This test has ID ….. Is there a way to either silence this line, or set an ID via the environment?

[craigfe]

AFAIK, there is no such existing feature. In Alcotest's own test suite, we strip such non-deterministic output with a separate binary. In addition to the random ID, we also have to account for:

• differences in printed filepaths on various platforms;
• variations in reported duration of the test run;
• some changes to OCaml's exception reporting for different OCaml versions – perhaps not an issue for you.

Additionally, Alcotest's default output format has been historically quite unstable, so snapshotting it while consuming it as a library may prove frustrating. I was going to suggest using .. --json 2>/dev/null, but it seems that --json still logs non-JSON lines to standard out. (This is likely a mistake, and can/should be fixed separately.)

I'm interested in knowing what information the snapshot is intended to hold: perhaps the binary contains both passing and failing cases and the goal is to record which is which?

[c-cube]

Indeed, so far I've been using a small shell script that captures the output and then uses sed and grep -v to remove parts of it.