You want to test a Java class that has dependencies on other classes and want to insulate your tests from changes in the behavior of those other classes.

Use Mocha, a Ruby mocking and stubbing framework that is included with JtestR. Mocha allows you to create instances of Java interfaces and classes that exhibit a specific behavior. Mock objects can be used in any type of test supported by JtestR. In Example 7-8, Mocha is used to create a mock instance ofjava.util.Collection, which is passed to an instance of java.util.ArrayList. This test validates the behavior of the retainAll() method, specifically that it calls thecontains() method on the supplied Collection object the correct number of times.

You want to write behavior-orientated tests for your Java code.

Use JtestR’s support for the RSpec Behavior-Driven Development (BDD) framework. RSpec is actually composed of two different frameworks for writing tests: the Spec framework and the Story framework.

RSpec Spec tests describe the behavior of an object through a series of assertions about the behavior of the object. These assertions are referred to as examples. The Spec file in Example 7-5 describes the behavior of the java.util.HashSet class.

You want to test your Java code using a more concise syntax than is available from Java testing frameworks such as JUnit and TestNG and want to ensure you follow some testing best practices, specifically limiting the number of assertions per test to one.

Use JtestR’s support for the Expectations framework. Like dust, Expectations provides a domain-specific language (DSL) for writing tests. Unlike dust, Expectations does not use the standard Test/Unit assertion methods. Instead, each test makes an assertion about the return value of the test. Example 7-4 contains the same tests seen in prior recipes using Expectations.