I am learning React+Redux now and came to the testing section. Many people use Mocha or Jest to test React components, so far so good, makes sense.
I previously have experience using Selenium and I see that Mocha is quite different in a sense that it tests just small parts of a web page(ReactComponents) and not the whole page. So in my understanding testing in Mocha is something like 'unit test' for components rather than long functional test with user stories and user behavior.
Considering testing a big project - does it make sense to use Selenium together with Mocha, even to the extent of almost copy-pasting tests? On a first glance we do something different with Selenium - i.e. we use the real browser, but on the other hand if we tested every possible thing in Mocha it should in theory be 'ALL PASSED' situation if tested in Selenium anyway, isn't it? So is it redundant to use both and should I just stick to one?