Pre-deployment activities
Environment design
The environment in which you test and evaluate your application affects how thoroughly you can test it, and how much confidence you have that those results accurately reflect what will happen in production. You might be able to perform some integration testing locally on developer machines by using services such as Amazon DynamoDB (see Setting up DynamoDB local in the DynamoDB documentation). However, at some point you need to test in an environment that replicates your production environment in order to achieve the highest confidence in your results. This environment will incur cost, so we recommend that you take a staged, or pipelined, approach to your environments, where production-like environments appear later in the pipeline.
Integration testing
Integration testing is the process of testing that a well-defined component of an application performs its functions correctly when it operates with external dependencies. Those external dependencies could be other custom-developed components, AWS services that you use for your application, third-party dependencies, and on-premises dependencies. This guide focuses on integration tests that demonstrate the resilience of your application. It assumes that unit and integration tests already exist that demonstrate the functional accuracy of your software.
We recommend that you design integration tests that specifically test the resilience
patterns you have implemented, such as circuit breaker patterns or load shedding (see Stage 2: Design and implement). Resilience-oriented integration
tests often involve applying a specific load to the application or intentionally introducing
disruptions into the environment by using capabilities such as AWS Fault Injection Service (AWS FIS)
Automated deployment pipelines
Deployment to, and testing in, your pre-production environments is a repetitive and complex task that is best left to automation. Automation of this process frees up human resources and reduces the opportunity for error. The mechanism for automating this process is often referred to as a pipeline. When you create your pipeline, we recommend that you set up a series of testing environments that get increasingly closer to your production configuration. You use this series of environments to repeatedly test your application. The first environment provides a more limited set of capabilities than the production environment but incurs a significantly lower cost. Subsequent environments should add services and scale to more closely mirror the production environment.
Start by testing in the first environment. After your deployments pass all your tests in
the first test environment, let the application run under some amount of load for a period
of time to see whether any issues occur over time. Confirm that you have configured
observability correctly (see Alarm precision later in this guide) so
that you can detect any issues that arise. When this observation period has completed
successfully, deploy your application to your next testing environment and repeat the
process, adding additional tests or load as supported by the environment. After you have
sufficiently tested your application in this way, you can use the deployment methods that
you previously set up to deploy the application into production (see Define CI/CD
strategies earlier in this guide). The article Automating safe, hands-off
deployments
Load testing
On the surface, load testing resembles integration testing. You test a discrete function
of your application and its external dependencies to verify that it operates as expected.
Load testing then goes beyond integration testing to focus on how the application functions
under well-defined loads. Load testing requires verification of correct functionality, so it
must occur after a successful integration test. It is important to understand how well the
application responds under expected loads as well as how it behaves when the load exceeds
expectations. This helps you verify that you have implemented the necessary mechanisms
to ensure that your application remains resilient under extreme load. For a comprehensive
guide to load testing on AWS, see Distributed Load Testing
on AWS
