fails:ENV.replace raises TypeError if a key is not a String
fails:ENV.replace raises TypeError if a value is not a String
fails:ENV.replace raises Errno::EINVAL when the key contains the '=' character
fails:ENV.replace raises Errno::EINVAL when the key is an empty string
fails:ENV.replace does not accept good data preceding an error
fails:ENV.replace does not accept good data following an error
