Acceptance testing ensures that the developed software product will meet the business needs of the Product Owner/customer. These business needs are captured by the user stories in the Product Backlog that the Product Owner helped to create and prioritize. Each user story needs to be refined with more details. This is done with the creation of the Acceptance Criteria for user stories during Backlog Refinement in preparation for the next Sprint Planning session.
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Following the instructions given here. Throughout the remainder of the project, your team will keep an up-to-date Acceptance Test Plan which is the set of all the user stories in the Product Backlog with their Acceptance Criteria and any specific test cases that you defined.