JMockit

JMockit is a handy set of tools that makes it easier to test your code using popular frameworks like JUnit or TestNG. It takes advantage of Java 5 SE's cool instrumentation feature (that's in the java.lang.instrument package) and uses the ASM library to tweak bytecode while your program runs.

Explore JMockit's Components

JMockit comes packed with six different components, and you can use them individually. Let’s break them down:

JMockit Core

This component is just a single class that has a few static methods. What’s great about it is that it allows you to swap out any method or constructor in another class with mock versions while your program is running!

JMockit Annotations

This part gives you some neat Java 5 annotations. You can set limits on how many times each mock should be called during testing, making it super easy to control your tests.

JMockit Expectations

This tool introduces a record/replay style for your tests. It helps keep things tidy and straightforward when writing tests, so they’re easier to read and understand.

JMockit Hibernate Emulation

This one’s pretty cool! It fakes the Hibernate 3 Core APIs, letting you run tests without needing a real database. You simply set a JVM argument to switch it on. When you're testing with this emulation active, no actual O/R mapping info is used, and all operations work against an in-memory database instead.

JMockit AOP

The AOP (Aspect-Oriented Programming) support lets you add advice before, after, or around any method or constructor. It's perfect for adding extra behavior without changing your code much!

If you want to dive deeper into JMockit and get these tools for yourself, check out this link.