Flaky ModelSpec

[ch1bo]

The ModelSpec is failing on some trace executions, leading to a flaky CI:

https://github.com/input-output-hk/hydra-poc/actions/runs/3188268110/jobs/5200728011

Last observed on commit: 2d8a6f0

   To rerun use: --match "/Hydra.Model/implementation respects model/"

Randomized with seed 1812008094

[ghost]

Another instance: https://github.com/input-output-hk/hydra-poc/actions/runs/3224136770/jobs/5274943489#step:8:626

  To rerun use: --match "/Hydra.Model/check conflict-free liveness/"

Randomized with seed 1098815834

[ghost]

Looks like we have a clear picture of why these errors happen:

• We try to post a NewTx with a value of 0 and there's not corresponding UTxO because the 0 value gets "folded" into an empty asset map.
• This happens because we initially commit a UTxO with a value of 0
• This happens because we can generate 0 ADA values commits which does not make sense

[pgrange]

I've just created this branch with a Model test that proves that we are currently generating UTxO with 0 Ada (and so fails):
https://github.com/input-output-hk/hydra-poc/tree/flaky_model_spec

cabal test hydra-node --test-options='--match Model'

[ghost]

Closed by #552 (hopefully)

[ch1bo]

So.. let's close this then until it re-appears.