What happens when integration testing fails? It's better to know that sooner than later and adjust accordingly to make sure the system as a whole works together. By bringing this testing as close to the front of the process as you can, it reduces the amount of mystery about how it will all work together later. By reducing mystery about how everything fits together, you substantially reduce stress.
Contrast that with making changes in a big batch and waiting until the end to put it all together. This approach risks creating components that work perfectly according to their specifications, but don't combine together to make a full system that works according to its specification. Figuring out that this is the case can be a long, painful, demanding process as many different groups, each responsible for different components, try to decipher which part isn't working correctly. With continuous delivery, you tackle integration problems sooner, which mean less stress.
By deploying more often, you reduce the number of untested assumptions, and you'll also now have much more regular communication between the two groups to figure out what's going on, what's working, and what's not. In other words, with continuous delivery, you talk to each other more often and you build up rapport. As rapport grows, people start talking. Both groups learn things about each other and begin to work together.
Contrast that with saying, "Here are the 50 changes I talked to you about three months ago. Make them run in production."
Who knows if both groups understand the impact of those changes?
There isn't any exchange of understanding and no acknowledgment of uncertainty, just a command to comply. With frequent, smaller changes, you talk more often — making mistakes from misunderstandings less common.
A lot of people think of continuous delivery as living on the edge, but as you've seen from these five points, it has just the opposite effect. Instead of increasing stress, continuous delivery lets everyone sleep better at night, meaning the end of all-nighters at the end of a big release cycle. Deployment, which was really taxing in the past, becomes routine and is no longer the taxing process it once was.
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