We use in-process ganache which throws on an RPC error. This means all of our tests get a nice revert error thrown when testing against ganache. This is not possible with RPC providers and a revert with reason result is returned. Our callAsync doesn't handle this and attempts to decode the revert with reason error log as a successful log, which results in an error while decoding.
This only works with our fork of ethers https://github.com/ethers-io/ethers.js/pull/188 and will need to be re-worked when updating to Ethers.js 4
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