Container

// Definition

An isolated runtime unit that packages an application with its dependencies, libraries, and configuration into a single portable artefact. Unlike VMs, containers share the host OS kernel and start in milliseconds. In testing, containers provide consistent, reproducible environments: the same Docker image that runs locally runs identically in CI. Common uses include spinning up databases, mock services, and headless browsers for automated test suites.

// Related terms

• Continuous Integration

  The practice of merging code changes to a shared branch frequently, with automated builds and tests running on every change. Catches integration issues early and keeps the main branch always shippable.

• Test Environment

  The infrastructure where tests run — hardware, OS, database, network, and configuration. Differences between test and production are a leading source of bugs that pass tests but fail in production.