Jupiter 
Package Description
org.junit.jupiter.api
JUnit Jupiter API for writing tests.
org.junit.jupiter.api.condition
Annotation-based conditions for enabling or disabling tests in JUnit Jupiter.
org.junit.jupiter.api.extension
JUnit Jupiter API for writing extensions.
org.junit.jupiter.api.function
Functional interfaces used within JUnit Jupiter.
org.junit.jupiter.engine
Core package for the JUnit Jupiter test engine.
org.junit.jupiter.engine.descriptor
Test descriptors used within the JUnit Jupiter test engine.
org.junit.jupiter.engine.discovery
Internal classes for test discovery within the JUnit Jupiter test engine.
org.junit.jupiter.engine.discovery.predicates
Internal predicate classes used by test discovery within the JUnit Jupiter test engine.
org.junit.jupiter.engine.execution
Internal classes for test execution within the JUnit Jupiter test engine.
org.junit.jupiter.engine.extension
Test extensions specific to the JUnit Jupiter test engine.
org.junit.jupiter.engine.script
Scripting support specific to the JUnit Jupiter test engine.
org.junit.jupiter.migrationsupport.rules
Extensions which provide (limited) support for JUnit 4 rules within JUnit Jupiter.
org.junit.jupiter.migrationsupport.rules.adapter
Simple wrappers for JUnit 4 rules to overcome visibility limitations of the JUnit 4 implementations.
org.junit.jupiter.migrationsupport.rules.member
Abstractions for members which can be targets of JUnit 4 rule annotations.
org.junit.jupiter.params
JUnit Jupiter extension for parameterized tests.
org.junit.jupiter.params.converter
ArgumentConverter implementations and their corresponding ConvertWith annotations.
org.junit.jupiter.params.provider
ArgumentsProvider implementations and their corresponding ArgumentsSource annotations.
org.junit.jupiter.params.support
Support classes for building providers and converters for arguments.
Vintage 
Package Description
org.junit.vintage.engine
Core package for the JUnit Vintage test engine.
org.junit.vintage.engine.descriptor
Test descriptors used within the JUnit Vintage test engine.
org.junit.vintage.engine.discovery
Internal classes for test discovery within the JUnit Vintage test engine.
org.junit.vintage.engine.execution
Internal classes for test execution within the JUnit Vintage test engine.
org.junit.vintage.engine.support
Internal support classes for test discovery and execution within the JUnit Vintage test engine.
Platform 
Package Description
org.junit.platform.commons
Internal common library of JUnit.
org.junit.platform.commons.annotation
Common annotations for the JUnit Platform.
org.junit.platform.commons.logging
Internal logging package.
org.junit.platform.commons.support
Maintained common support APIs provided by the JUnit Platform.
org.junit.platform.commons.util
Internal common utilities for JUnit.
org.junit.platform.console
Support for launching the JUnit Platform from the console.
org.junit.platform.console.options
Configuration options for JUnit's console launcher.
org.junit.platform.console.tasks
Internal execution tasks for JUnit's console launcher.
org.junit.platform.engine
Public API for test engines.
org.junit.platform.engine.discovery
Concrete selectors and filters to be used in discovery requests.
org.junit.platform.engine.reporting
Classes used by test engines to report additional data to execution listeners.
org.junit.platform.engine.support.descriptor
TestDescriptor-related support classes intended to be used by test engine implementations and clients of the launcher.
org.junit.platform.engine.support.filter
Filter-related support classes intended to be used by test engine implementations.
org.junit.platform.engine.support.hierarchical
Support classes and base implementation for any TestEngine that wishes to organize test suites hierarchically based on the Node abstraction.
org.junit.platform.launcher
Public API for configuring and launching test plans.
org.junit.platform.launcher.core
Core support classes for the Launcher including the LauncherFactory and the LauncherDiscoveryRequestBuilder.
org.junit.platform.launcher.listeners
Common TestExecutionListener implementations and related support classes for the Launcher.
org.junit.platform.launcher.tagexpression
The tag expression language parser and related support classes.
org.junit.platform.runner
Runner and annotations for configuring and executing tests on the JUnit Platform in a JUnit 4 environment.
org.junit.platform.suite.api
Annotations for configuring a test suite on the JUnit Platform.
org.junit.platform.surefire.provider
Maven Surefire provider for the JUnit Platform.