Hi,
When a string value is received while an NSURL value expected, fail error message would be like this:
expected: http://myurl.com, got: http://myurl.com
This is because EXPDescribeObject uses -description method of nsobject, which prints string value of url for NSURL class.
Would adding also class type of values be appropriate? This way, description message could be more descriptive.
I can help with a PR if this is a proper improvement for you.