A test suite with 50 integration test classes runs sequentially in 10 minutes. Configured for parallel execution across 4 threads, it completes in 3 minutes. Parallel test execution with Testcontainers requires careful data isolation — tests running simultaneously against the same database will step on each other’s data without it. This article covers JUnit 5 parallel configuration, container sharing strategies, and data isolation techniques. What You’ll Learn JUnit 5 parallel execution configuration with junit-platform.