This is the fastest way if you are already writing code. IntelliJ can detect a missing JUnit library and "download" it for you automatically.
If you are using a build tool like Maven or Gradle, you shouldn't download JARs manually. Instead, you define them in your configuration files. For Maven ( pom.xml ): how to download junit in intellij
Learning how to download and configure in IntelliJ IDEA is a foundational step for any Java developer. While "downloading" might sound like a manual task, modern development environments typically handle this through built-in dependency management or automated IDE features. This is the fastest way if you are already writing code
Setting up JUnit with IntelliJ IDEA [duplicate] - Stack Overflow Instead, you define them in your configuration files
After saving, click the icon (the small "M" with a refresh arrow) in the top-right corner to download the library. For Gradle ( build.gradle ): Add this line to your dependencies block: