Introduction
A few years back, when software development strategies such as the Waterfall model were prominent, the testing phase used to start after the whole development phase is complete and later came the release. We have come a long way since then after the adoption of Agile and DevOps practices. However, UI automation typically still lags behind the sprint.
The reason is that Agile and DevOps approach doesn't allow a lot of time for comprehensive test creation between code completion and release. You may need to depend heavily on manual testing practices in order to guarantee minimum coverage. One of the ways to avoid this is to start the testing process very early in the sprint.