In an embodiment, the effect of signal phase difference on a memory system is tested for various operating states. The various operating states may be represented as respective sample points on a plane defined by a range of values for a difference in signal phases and a range of values for another operating state parameter. In various embodiments, sample points for a round of crosstalk testing may include two sample points which are offset from the same reference point on the plane along different respective axes, where the axes are oblique to one another.