The semiconductor equipment company's fourth-quarter sales and earnings exceeded expectations.As a test and quality control equipment manufacturer for the semiconductor industry, Aehr Test Systems (AEHR -1.82%) and its investors know all about the industry's cyclicality. Customers cut chip orders dramatically in bad times, only to hike them aggressively in good times. That's reflected in the stock price volatility, which implies risk; this week, the risk was on the upside.Why Aehr Test Systems stock outperf ...