I think the compsci departments need a new course titled something like "Reading Code" where one learns to read any code fast and efficiently like they would a newspaper article or novel. Now that would be useful.
If the course is an elective it's probably better (more motivated students).
The hard parts are (1) understanding the scenarios the code covers, (2) interpreting error messages and edge cases coming from it.
Even better, in fact: one can misread a book with, usually, no reasonable way of determining the extent of one's misreading (see https://news.ycombinator.com/item?id=18380366 for a current front-page example); whereas, when one (mis)reads code, there is always at hand a way to test the accuracy of one's reading (and perhaps find out thereby, in the presence of a sufficiently detailed specification, that the programmer also 'misread' it!).