chore: explicitly test all errors

[jamesondh]

Motivation

Make tests more comprehensive.

Explanation of Changes

Added and modified tests to explicitly check for each error defined in each contract's error.rs. For errors that require testing using multiple contracts, the error is tested in the integration tests packages.

Failing checks are caused by an outdated rust version using a previously unstable feature. They pass with a bumped version: #77

Testing

N/A

Related PRs and Issues

Closes #58

[Thomasvdam]

I think this one clashes with #78 ? Maybe we should merge that one first and then see what the conflict damage is, provided the approach in #78 is desired.

[jamesondh]

@mariocao I had to add anyhow back in this PR (despite Menna removing it as per your feedback in #78) to be able to get specific errors in the integration tests via res.unwrap_err().downcast_ref::<ContractError>(). I also tried replacing these with a #[should_panic] attribute, checking for the error enum variant, (as used in some unit tests) but the error in the integration tests only outputs the error message.

For example, in the unit tests I can use #[should_panic(expected = "IneligibleExecutor")] but in the integration tests I would have to use #[should_panic(expected = "Caller is not an eligible data request executor")], which I think is strange and inconsistent. Obviously this is a pretty minor issue but I think the anyhow dependency makes the integration tests just a bit more readable/maintainable 😅