Message chain unit tests

[radojevicMihailo]

Prerequisites

Please answer the following question for yourself before submitting a feature request.

• [ ] I checked to make sure that this request has not already been filed

Motivation

Is your feature request related to a specific problem? Is it just a crazy idea? Tell us about it!

Details

Please describe your feature request in detail.

Make sure that you have reviewed MACI's Contributor Guidelines

[radojevicMihailo]

Implementation of unit tests covering all modifications to smart contracts, client service, and circuits introduced with message chain implementation