`length` for localStorage is not updated immediately on native, which
suggests some caching is involved for a period of time (probably for
performance reasons to avoid reading the file everytime the prop is read),
or it doesn't block like the rest since the write is asynchronous, making
it unreliable to test, which is why the tests for it are basic.
Signed-off-by: Gabriel Ivăncescu <gabrielopcode@gmail.com>