In order to deliver value in short cycles sustainably, agile teams (and organisations) put a strong emphasis on building quality into their products and services, as opposed to “inspecting” (aka "doing QA on") quality after the event (which is too late). Quality, including testing, happens right from the start via some core daily quality practices and principles.

Not doing the above often leads to:

• in the case of software, the codebase becoming increasingly difficult to change, and susceptible to regression defects
• compromises and trade-offs on quality being made due to time pressures forcing quality (or anything left to the end) to be an after-thought, done poorly or not at all
• products and services which have poor quality from the customer’s point of view, i.e. they do not meet the customer’s needs
• slowing the team down because they spend more time fixing bugs and firefighting, and thus have less capacity for value-adding work.