Most recipes for pizza dough tell you to keep kneading until the dough is smooth and elastic. That's simple enough, right? The dough goes from being a clumpy, lumpy mass to something that is cohesive and, well, smooth. And instead of tearing off in ragged chunks, it begins to stretch. The more you knead, (or the longer it rests, for long-fermented doughs) the stretchier it gets. But when do you stop kneading? How elastic does it need to be? Oh, if only there was a simple test for checking the elasticity of the dough! But wait! There is! It's the Windowpane Test!