It's unstated but are we to understand that he set up the test to send money to a test account which was his own personal account?
Funny enough, in a fintech I worked for, developers and QAs actually used their own personal credit cards and bank accounts for testing.
Interestingly, they also needed to test ApplePay, but the laptops didn't allow for adding their personal iCloud accounts. So someone in the development team got the "admin" password and distributed among devs and QA team, and they all had unprotected laptops. They probably still do.
So taking your own account during early development can make sense. Leaving it in is probably a bad idea tho.