Talking for Python version.

Their could be REAL test cases . Those provided are :

• not working out of the box (test.expect_equal does not exist,test.expect do)
• provide no edge case at all (words with length == width, multiple spaces between words, ...)

Since you have to use the submit button to actually test your solution, some message could be more explicite and include line.
Example :"Line starts or ends with a space" Which line ? How was it formated ?