Add integration tests

[ekatef]

The PR adds a check on propagation along the workflow of the values which must be invariants according to conservation laws.

Checklist

• I consent to the release of this PR's code under the AGPLv3 license and non-code contributions under CC0-1.0 and CC-BY-4.0.
• I tested my contribution locally and it seems to work fine.
• Code and workflow changes are sufficiently documented.
• Newly introduced dependencies are added to envs/environment.yaml and doc/requirements.txt.
• Changes in configuration options are added in all of config.default.yaml and config.tutorial.yaml.
• Add a test config or line additions to test/ (note tests are changing the config.tutorial.yaml)
• Changes in configuration options are also documented in doc/configtables/*.csv and line references are adjusted in doc/configuration.rst and doc/tutorial.rst.
• A note for the release notes doc/release_notes.rst is amended in the format of previous release notes, including reference to the requested PR.

[ekatef]

The implementation is currently very rough, and the primary application is to provide a tool to check consistency of the current workflow.

Testing for the tutorial test case, has given satisfactory results for "physical" load, as well as solar and offwind potential. However, onwind potential has increased ater simplification and clustering by about ~30% (22363710.2206911 for elec.nc vs 29223050.6195861 for elec_s_6).

[davide-f]

Great! :D I'm wondering if this would be greatly placed in a test folder or potentially a validator procedure. what do you think?

[ekatef]

Great! :D I'm wondering if this would be greatly placed in a test folder or potentially a validator procedure. what do you think?

Totally agree that ideally it should be added to the tests and just satisfied under all the conditions.

Currently, it looks like currently we may have some flaws should be fixed first. In particular, it relates to the renewable potential which must be investigated better. The relevant part is weighting procedure in PyPSA which may probably need some correction coefficients.

I'm transforming this PR into a draft for now 🙂