Test case for Speaking ALT text
This test case illustrates several methods of specifying ALT text for images. It can be used to determine exactly what screen readers or other assisstive technology provide for various cases.
Immediately following is an image with no ALT text at all. 
Immediately following is an image with ALT text of only two quote characters.
Immediately following is an image with ALT text of quote space quote.
Immediately following is an image with descriptive ALT text.
Comments are welcome at the essay about this topic in the Access Matters blog.