Mock ALL specs for testing, to avoid having to adapt to changes in published specs

[tripu]

eg, I just had to update the metadata of a couple specs used for testing, to avoid new errors (because there was a new version published, and suddenly latest ≠ previous).

We should either pick only mature, stable specs for tests (eg, not WDs being updated often via Echidna), or mock all specs (with the added benefit of relying less on a connection to the internet to run the tests).