Add unit tests to update functions (use mocking to make this possible)

[JasoonS]

We can use something like this: https://codewithhugo.com/jest-mock-spy-module-import/ / https://jestjs.io/docs/en/manual-mocks
or something more bare bones? https://www.npmjs.com/package/mock-require (or https://github.com/theKashey/rewiremock? which is called the best library for this here: https://itnext.io/how-to-mock-dependency-in-a-node-js-and-why-2ad4386f6587)

We can use jest since even though this is assemblyscript since assemblyScript is a subset of typescript.