EasyMock is a Java library that simplifies the creation of mock objects for unit testing purposes. It allows developers to mimic complex behavior in the system by simulating objects and defining their expected behavior during testing. EasyMock supports a range of features, including strict and default mocks, argument matchers, and verification of method calls, helping to streamline the testing process and improve code reliability. Designed for ease of use, EasyMock aims to facilitate effective test-driven development in Java applications.