Is it possible to ignore the prototype when doing object comparisons?

[opensourcegeek]

I recently moved some code that had Object.assign(Object.create(null), { prop1: 1 }) to just properties on the class, where the class holds this.props1 = 1. Then the assertions started failing.

   expect(postDataStub).to.be.calledOnceWith(dataObject);

If I do a Object.setPrototypeOf(objInstantiatedFromClass, null) then tests pass again. The real test has nested properties. I just wanted to see if I can somehow get away by telling sinon to ignore prototype methods.