  We characterize minimal measurement setups for validating the quantum
coherence of an unknown quantum state. We show that for a $d$-level system, the
optimal strategy consists of measuring $d$ orthonormal bases such that each
measured basis is mutually unbiased with respect to the reference basis, and
together with the reference basis they form an informationally complete set of
measurements. We show that, in general, any strategy capable of validating
quantum coherence allows one to evaluate also the exact value of coherence. We
then give an explicit construction of the optimal measurements for arbitrary
dimensions. Finally, we show that the same measurement setup is also optimal
for the modified task of verifying if the coherence is above or below a given
threshold value.
