External beta testing offers developers their first glimpse at how users may actually interact with a program. Copies of the program or a test URL, sometimes accompanied with letter of instruction, are sent out to a group of volunteers who try out the program and respond to questions in the letter. Beta testing is black-box, real-world testing. Beta testing can be difficult to manage, and the feedback that it generates normally comes too late in the development process to contribute to improved usability and functionality. External beta-tester feedback may be reflected in a README file or deferred to future releases.