When i first started coding, i listened to the senior coders for hours on how the reservations, sales, and acct software worked together. That told me what files to code.
Then i went and stayed in the Sales floor for a month and found out how it really worked.
I went to the Accounting dept. and found the workarounds they used every day, to bypass our software.
I even made a sale to test the whole thing!
Long story short, coders don't use software. Seriously, they don't. They don't know how, because they know how it works.
they bypass things in their head, they don't answer to anybody. Go find the Standard Operating Procedures and see how closely they are followed. Go do the job, be the tester. Everything else is useless assumption.