Inversion of Control is a common phenomenon that you come across when extending frameworks. Indeed it's often seen as a defining characteristic of a framework.
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These are complicated cases of inversion of control, but you run into this effect in much simpler situations. A template method is a good example: the super-class defines the flow of control, subclasses extend this overriding methods or implementing abstract methods to do the extension. So in JUnit, the framework code calls setUp and tearDown methods for you to create and clean up your text fixture. It does the calling, your code reacts - so again control is inverted.
There is some confusion these days over the meaning of inversion of control due to the rise of IoC containers; some people confuse the general principle here with the specific styles of inversion of control (such as dependency injection) that these containers use. The name is somewhat confusing (and ironic) since IoC containers are generally regarded as a competitor to EJB, yet EJB uses inversion of control just as much (if not more).
Etymology: As far as I can tell, the term Inversion of Control first came to light in Johnson and Foote's paper Designing Reusable Classes, published by the Journal of Object-Oriented Programming in 1988. The paper is one of those that's aged well - it's well worth a read now over fifteen years later. They think they got the term from somewhere else, but can't remember what. The term then insinuated itself into the object-oriented community and appears in the Gang of Four book. The more colorful synonym 'Hollywood Principle' seems to originate in a paper by Richard Sweet on Mesa in 1983. In a list of design goals he writes: "Don't call us, we'll call you (Hollywood's Law): A tool should arrange for Tajo to notify it when the user wishes to communicate some event to the tool, rather than adopt an 'ask the user for a command and execute it' model." John Vlissides wrote a column for C++ report that provides a good explanation of the concept under the 'Hollywood Principle' moniker. (Thanks to Brian Foote and Ralph Johnson for helping me with the Etymology.)
