I have a class "SomeService" which isn't exported. I export the instance which can be used to call functions on it. Basicly a singleton. Here the example

export const someService = new SomeService(otherService.getConfigObject());

Now when I write unit tests (Currently using sinon and mocha) I can't really mock the otherclass like i would like to. In the beforeEach the instance is already created with a real object.

The only thing that worked is

1. import sinon
2. stub otherClass
3. import someService instance

Which seems very hacky and my formatter (correctly) puts the imports on top.

Is there a convenient way to mock the constructor or otherClass to give my instance a mockConfig? Should i reconsider the architecture choice to export created instances?