TL;DR

In order to start testing a program in Agile team, you first need to understand what is software program. This post will explain, using examples, what is software program according to Black Box Software Testing.

Computer Program

Computer science teaches that a computer program is:

A program is a set of instructions for a computer.

That is like defining that a beer is:

Beer is a mixture of water, malted barley, a brewer's yeast and hops.

But better definition would be:

A beer is something built for people to quench thirst.

Focus of second definition is beer purpose, not beer materials, and beer stakeholders, people. Stakeholder is any person affected by project outcome, product actions and service effects. In Agile team, we must move from narrow focus on the machine.

Black box Software Testing Definition

A computer program is a COMMUNICATION among HUMANS and COMPUTERS, distributed over SPACE and TIME, that contains INSTRUCTIONS that can be executed by computer. The POINT of computer program is to provide VALUE to STAKEHOLDERS.

First definition has only two keywords: instructions and computer. Second one adds six more keywords: communication, humans, space, time, point, value and stakeholders. You probably encountered those keywords in your Agile team: communication (email, Skype, Slack, sms), humans (product owner), space (remote team), time (remote team in different time zone), point (what is purpose of this feature), value (is this purpose fulfilled), stakeholders (client, product owner, developer, fellow testers).