Sinon: Stubbing const objects

[tomatau]

Working in a node or es6 environment, many exported objects are defined as const, this is considered a good practice to avoid breaking modules of the application.

However - when testing, these const defined objects can't be stubbed out which seems problematic from a unit testing perspective.

I guess there's nothing that can happen from the perspective of Sinon to resolve this problem as it needs to mutate the target of stubbing/spying in order to change it in the test's context.

Are there any suggested approaches that could be used to somehow disable the behaviour of const imports/requires during test?

I've tried to stub/mock at import time but this doesn't seem to play nicely with build systems such as webpack/babel for numerous reasons so have settled with the regular sinon stubbing approach (which I also prefer) but I'm reluctant to change my exported objects to be mutable!

[mroderick]

For stubbing dependencies in node, I usually use one of these

• https://github.com/thlorenz/proxyquire
• https://github.com/jhnns/rewire

Then you can redefine what the dependency is before loading your code.

These work really well for me. Are those the solutions you have tried?

[tomatau]

Have tried both. Webpack doesn't play nice as it doesn't use the node require directly.

Closest to a solution like this was to use the inject-loader plugin for webpack - this doesn't play well with babel loader.

[mroderick]

This ticket is really a usage question, and not directly related to Sinon.JS either. Please post it to the ~Sinon.JS mailinglist~ Stack Overflow using the sinon tag, so the bigger community can help answer find a solution.

[freewind]

Thanks for this question and your answer. I searched sinon stub const and reached here, and your suggestion proxyquire solved my problem. If it's in the mailinglist, I think I can't find this answer in time.

[d2lam]

rewire works wonderfully! Thanks!