Here at Sagepay we work in weekly iterations, i.e. the aim at the end of every weekly iteration is to deliver something new to the user; whether it be a developer, a customer or the manager of a business.
To help with this, we use Jenkins as our continuous integration tool. Once development is complete (we work on branches), the new code is merged to master. This will trigger builds on the pipeline that will deploy to the development environment and run the e2e tests (also on dev). The deployment to the QA environment is manual; I do this when one particular story is complete and is ‘releasable’. I run some basic manual tests on QA to make sure basic flows are working as expected (I have a checklist!).
What I have learnt when you are working in this way is that you have to have 100% confidence in the automated tests that are on the pipeline and the coverage that these tests have. Otherwise, it would not be possible to release weekly and QA would almost always block a release if it were manual.
This leads on to pair programming. When we have decided which stories we are going to work on in a sprint, I pair with a developer and start discussing what tests we should have for this particular story. This usually starts off by looking at the acceptance criteria as a baseline. We write some basic tests, e2e tests are easiest to write first and make them fail. Unit tests/integration tests follow. I will be writing a separate blog post about the different types of testing and the purpose of each level of testing. Once these new tests have passed and regression tests have passed, I am confident that the new code we will release will not break anything.
One thing to note: my focus is not to test everything and anything. It is to focus on what matters to the user and what they will do. How are they using the application? That way you ensure you test what is necessary and what will give you the most useful feedback.