Sorry I should have been more precise. I don't mean mutation, but taking the data and producing a new (potentially unstable) reference to pass on. Mutating data in react results in under not over firing.

It is practically impossible to have full coverage of all code paths in integration tests, since there is a combinatorial explosion of paths. In a case where you have 3 components each with 3 paths you have 27 unique paths. And no app is that simple in practice. It gets out of hand quickly.