I have a migration module that imports data from a CSV. I've steadily been adding code to the module and fields to the CSV, and it's always worked, albeit sometimes only after some work. But now there's one profile2 profile among the many I'm importing to in which the text fields don't get any data successfully imported to them. This happens even when I just put '1' or '0' for them in the CSV. Oddly, the non-text fields in the profile2 profile import fine, even though they're later in the CSV and the module code.
My question is how I go about debugging this. I couldn't find a 'how to debug Migrate' page in the documentation or on the web. I've found Migration::displayMessage, but what can I print via this to show what data's been mapped to these fields from the CSV? I just get the abstract mapping structure without any data from my CSV when I run
Migration::displayMessage('<pre>'.print_r($this, TRUE).'</pre>', 'debug');