Accelerating feedback loops are an important devops principle: the sooner you find a bug, the cheaper it is to fix it.
While developing your application, you’re typically going through a cycle: write code, build, deploy into a test environment, run tests, fix, repeat. The build and deploy stages of this cycle are idle, unproductive time where you’re simply waiting. As a project grows, these stages get slower and slower. Once they’re slow enough, you end up context switching to another task, while waiting, and that makes it harder to get back into the right context and fix any bugs you find in testing.