Tuesday, 22 December 2015

Acceptance Test Is Not an Environment

In a traditional software development process where you did analysis, development and then testing, there is often the use of shared environments, and therefore there is often a one-to-one relationship between the name of the environment and the type of testing performed. For example UAT (User Acceptance Testing) tends to come right at the very end of the process just before production. If you are working on a back-end system there may well be no “U” in the UAT and so it really just becomes a more production-like test environment.

In a modern development process there is more of a distinction between the type of tests we are running and the environment in which we are running them. We are always trying to achieve a balance between getting the fastest feedback possible on whether our changes are correct, whilst still ensuring that enough of the system is being tested in a manner similar to production so that we minimise any problems due to environmental differences.

In my C Vu article “The Developer’s Sandbox” I described a number of different ways that you might partition a system (and test data) to allow a variety of different levels of non-unit testing. In essence I am mostly interested in running fast, automated test suites in some isolated manner to gain rapid feedback. However I also like to do a bit of manual exploratory testing, especially when making changes around deployment or infrastructure code. And demoing new features is also important too to ensure that we’re building “the right thing”.

What I’ve found is that there is often some confusion when talking about testing that conflates the suite of tests being exercised with the configuration of the system it’s being run on. For example I will try and run every automated test possible on my local machine before committing my changes. This means I’m probably running some combination of unit, component, integration, acceptance and system tests against a variety of mock and real components and services depending on how expensive or not they are to use.

Similarly on the build server we will run exactly the same suite of tests but because we have more time we can use the real dependencies where possible and only rely on mocks where we have to. The closer the code gets to production the closer the test environment has to get to production too.

As a consequence this means there is no one-to-one relationship between the test suite configuration and the environment where it is run. By default we tend to optimise for the developer feedback loop which means the out-of-the-box configuration is usually “localhost” everywhere [1]. In contrast the build server, development and test environments will likely have real networks, databases, message queues, etc. in play and so the same suite of tests will increase the amount of infrastructure and integration for a more production-like quality, perhaps at the expense of performance. The point is that we aim to run the same tests and only vary the configuration. Hence when talking about automated testing it may require us to qualify it with the environment configuration we might be running with to avoid confusion.

One natural observation might be that it’s not right to call the running of the acceptance test suite on a developer’s local machine “acceptance tests” as some element of the “acceptance” must come from it being run in a more-production like manner. Whilst I get the sentiment, I think that misses the point about developer’s leveraging the traditionally more costly tests in a constrained, but by no means useless environment, to gain earlier feedback around the functional behaviour. No, it doesn’t mean it’s signed-off and ready for production just because it works on my machine, but it does mean that at a fundamental level the change is sound and worthy of pushing further down the deployment pipeline.

[1] I always say that I should be able to unplug from the network and go out into the garden where there is no Wi-Fi and still be able to write code and have a high degree of confidence that it works. Modern tooling (and a sane approach to developer licensing) makes that possible even when databases, message queues, etc. are in the equation without having to restrict ourselves to relying solely on unit testing.

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