Sorry, should have written this in the first email. I think another thing I would do to debug is fmt.Printf as many relevant variables as you can think of to see if any of them don't look right, but only make this happen when you have a failed test (where you would t.Fail()).
-William On Wednesday, August 2, 2023 at 2:01:58 AM UTC-4 Jochen Voss wrote: > Dear all, > > Recently I find quite often that after "go test -fuzz" reported an error, > the command shown to re-run the test does not reproduce the failure. For > example, just now I got the following: > > voss@dumpling [..nt/tounicode2] go test -fuzz FuzzToUnicode > fuzz: elapsed: 0s, gathering baseline coverage: 0/2 completed > fuzz: elapsed: 0s, gathering baseline coverage: 2/2 completed, now fuzzing > with 10 workers > fuzz: elapsed: 3s, execs: 280461 (93481/sec), new interesting: 24 (total: > 26) > fuzz: elapsed: 5s, execs: 410320 (72348/sec), new interesting: 60 (total: > 62) > --- FAIL: FuzzToUnicode (4.80s) > --- FAIL: FuzzToUnicode (0.00s) > tounicode_test.go:129: template: tounicode:26:2: executing > "tounicode" at <Single $cs .>: error calling Single: runtime error: integer > divide by zero > > Failing input written to testdata/fuzz/FuzzToUnicode/2566873a28045c1b > To re-run: > go test -run=FuzzToUnicode/2566873a28045c1b > FAIL > exit status 1 > FAIL seehuhn.de/go/pdf/font/tounicode2 4.957s > voss@dumpling [..nt/tounicode2] go test -run=FuzzToUnicode/2566873a28045c1b > PASS > ok seehuhn.de/go/pdf/font/tounicode2 0.122s > > The fuzzer reported a failure, and when I re-run the test I get a "PASS". > > How to debug such a problem? > > I understand that my fuzz function may somehow be non-deterministic, but > so far I have not found any cause of non-determinism and re-running the > test 10 times gives me 10 passes. Also, for a bug the fuzzer reported > earlier, I found it very hard to believe that the given input could make > the fuzz function reach the site of the error message. Could it be that > the fuzzer sometimes looses track of which input belongs to which fuzzing > run, and then reports the wrong input? > > If somebody wants to play with this, here is how to reproduce (up to > randomness) the fuzzing run shown above: > > git clone https://github.com/seehuhn/go-pdf.git > cd go-pdf/ > git reset --hard 26c235ad > cd font/tounicode2/ > go test -fuzz FuzzToUnicode > > Any suggestions on how to debug such errors would be most welcome. > > Many thanks, > Jochen > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/68399541-7aea-4fcb-81e6-d39542643553n%40googlegroups.com.
