The Wikipedia article on gemination claims that gemination of /t/ is the distinguishing factor between the pronunciation of the two phrases night train and night rain.
In my whole life, I've almost never heard the final /t/ in night and the initial /t/ in train articulated the same way. The initial /t/ in train is affricated due to it being in the /tr/ cluster, while in night the /t/ is either a typical English T /t/, unreleased [t̚] or glottalized. They are distinct enough.
I don't think this minimal pair is distinguished by gemination in practical use, as far as I know. How is this pair really distinguished? Is there really gemination there?