This document provides an overview of how to use Mockito to create mock objects and define their behavior in tests. It explains how to create mocks with mock(ClassToMock.class), define return values and exceptions with when(method()).thenReturn()/thenThrow(), and verify mock interactions with verify(mock).method(). It also covers using @Mock annotation and initMocks() to initialize mocks, and matchers like eq() to verify argument matching. The document concludes with some Eclipse IDE tips to help with Mockito development.