What i mean is...
An ester is a compound, with properties, one of which, we assume, is solubility in methanol.
Which is what we do to test for esters (yep, i know you know this!)
So, we have a test. If it dissolves in methanol, we can, until proven otherwise, assume that they are esters. If they dont dissolve in methanol, then we can assume that they are not - regardless of their melting point : )