golden tests

[mzihlmann]

Description

adding a new kind of integration tests "golden tests"
The new features that come up are often concerned with performance improvements. These improvements are taken by not following the Dockerfile to the letter, but reorder and skip instructions where possible. It is both difficult to mentally model what exactly happens with an optimization and difficult to write tests that verify an optimization is indeed taken. Golden tests come to the rescue, basically kaniko learned a new --dryrun flag, which lets it print a plan instead of running commands. The plan shows what kaniko would be doing, this is after all optimizations were applied, in a sort of "intermediate representation". We can now simply compare the plan kaniko generates to a "golden plan" from a previous run and if there is a diff we most likely have a bug.

This will bring in a new dependency yaml. maybe we should separate productive and testing 3rparty?

[mzihlmann]

we could consider switching to toml, that would drop ~10k lines of dependencies as yaml is heavy

[mzihlmann]

refactored it to no longer use yaml files, but instead go files directly. This is not only simpler in terms of dependencies but allows us to update plans automatically too. so a win win.

[mzihlmann]

now that the dockerfile is separate to the test definitions, we could even consider referencing dockerfiles from integrationtests, this way we would always ensure that both plan is correct and we can indeed build the dockerfile too.