If you say something like

"If you like me, you'll buy flowers for me."

Then it follows that if that person does not buy flowers for you, he certainly does not like you. (MT)
But if he buys flowers for you, he may still not like you.

Unless you mean something like

"If you buy flowers for me, it means you like me."

Then it follows that anyone who buys you flowers like you(MP), but people who don't buy you flowers may like you too. That sounds pretty narcissistic.

Or maybe you mean

"Iff you like me, you'll buy flowers for me."

Then it follows that anyone who buys you flowers like you, and anyone who doesn't buy you flowers don't like you. Nice and simple. Too simple perhaps.

Oh bother.

Which leads me to scientific statements!

"If theory X is correct, A occurs."

Then it follows that if A does not occur, theory X is certainly not correct(MT), but if A occurs, X isn't neccessarily correct.

But which scientific theory to take?

"If theory X is correct, A and B occur."
"If theory Y is correct, A, B, C, D, E and F occur."
"A, B, C, and D occurs."
(You are not sure if E and F occurs)

Logic gives no answer.