You can't really unit test blurry text.

Sure you can. Just render the glyphs into a framebuffer and check the ratio of opaque pixels to semi-transparent ones. The more transparency the blurrier. But I agree with the poster below that it is usually to much trouble and only worth it if your software is deep down in the stack. For example, if you are writing a text rendering system it would make sense for such tests but not otherwise.

I agree, he would only have caught that if he were unit testing his UI, and usually doing that is more trouble than it's worth.