Technical Debt. Technical Debt Iterations. If the team does not pay attention to quality, it will soon become impossible to release anything rapidly. Perform frequent incorporation of work into the whole, no matter the product, and then retest to determine that the entire product still works as intended.
Employ system-level testing for end-to-end information and unit testing for the building blocks. In between, understand if there is a need for integration testing and where. For non-software projects, consider how to “test-drive” the team's designs. Hardware and mechanical projects often use simulations for interim tests of their designs.