Faith is a producer. There's always evidence when faith is in play.
At first, it creates an unusual response from those who live by faith. And eventually, it creates the promise they are believing for.
So, to determine if you are living by faith, you can't wait for the result. You first have to examine your response.
Let's use generosity as an example. Faith produces unusual generosity.
While most people look for the minimum they are obligated to give, those who live by faith always give their best. Not because they have to, but because they want to.
This is actually one of the primary indicators of whether you live by faith or not.
Those trying to figure out the minimum amount required to keep God happy are not pleasing God. It's not because He wants more, but because He wants faith.
And faith produces unusual generosity. There's no way around it.