The idea of dependency injection is to make every dependency a parameter of the function.
At the moment, our createUser function relies on entities outside of its parameters; this includes the create function and the ValidationError class. If we were to use dependency injection, we'd modify our createUser function to have the following structure:
function createUser(req, res, db, create, ValidationError) { create(req) .then(onFulfilled, onRejected) .catch(...)}
Then, we would be able to inject the following dependencies from our tests:
...import ValidationError from '../../../validators/errors/validation-error';import createUser from '.';const generateCreateStubs = { success: () => stub().resolves({ _id: 'foo'})}describe('create', ...
