March 2025
Intermediate to advanced
202 pages
4h 45m
English
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Testing Projectors
Projectors produce external state, or state that’s designed to be consumed by third parties. Since this state is part of the public API of the system, you need to write tests that assert that the shape of the projections matches what you expect.
It’s tempting to have your projector write the projected state directly to the external data store. When building examples and prototypes, it’s often much easier to simply write the projection out during processing. But when it comes time to test, such a design pattern makes the projector “effectful.” Writing the data ends up being a side effect of processing events.
It’s much more testable (and arguably cleaner) if the projectors return the new projection as a result of processing ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.