To ensure that the build and test steps execute consistently, we should run them inside a container, which is an ephemeral, pre-configured, isolated environment.
A container is similar to a virtual machine, but uses fewer resources and is quicker to provision. Creating containers is cheap; this allows us to create containers, run the tests, and then discard them afterward.
We will dive more in-depth into Docker in Chapter 17, Migrating to Docker; for now, it's sufficient to understand that a Docker container provides an isolated and consistent environment for us to run our builds and tests.
Docker is the most popular container framework out there, and we will run our builds and tests inside Docker containers. In ...
