junit4.4_test

## Summary of Changes in version 4.4 ## JUnit is designed to efficiently capture developers' intentions about their code, and quickly check their code matches those intentions. Over the last year, we've been talking about what things developers would like to say about their code that have been difficult in the past, and how we can make them easier. ### assertThat ### Two years ago, Joe Walnes built a [new assertion mechanism][walnes] on top of what was then [JMock 1][]. The method name was `assertThat`, and the syntax looked like this: [walnes]: http://joe.truemesh.com/blog/000511.html [JMock 1]: http://www.jmock.org/download.html assertThat(x, is(3)); assertThat(x, is(not(4))); assertThat(responseString, either(containsString("color")).or(containsString("colour"))); assertThat(myList, hasItem("3")); More generally: assertThat([value], [matcher statement]); Advantages of this assertion syntax include: - More readable and typeable: this syntax allows you to think in terms of subject, verb, object (assert "x is 3") rather than `assertEquals`, which uses verb, object, subject (assert "equals 3 x") - Combinations: any matcher statement `s` can be negated (`not(s)`), combined (`either(s).or(t)`), mapped to a collection (`each(s)`), or used in custom combinations (`afterFiveSeconds(s)`) - Readable failure messages. Compare assertTrue(responseString.contains("color") || responseString.contains("colour")); // ==> failure message: // java.lang.AssertionError: assertThat(responseString, anyOf(containsString("color"), containsString("colour"))); // ==> failure message: // java.lang.AssertionError: // Expected: (a string containing "color" or a string containing "colour") // got: "Please choose a font" - Custom Matchers. By implementing the `Matcher` interface yourself, you can get all of the above benefits for your own custom assertions. - For a more thorough description of these points, see [Joe Walnes's original post][walnes]. We have decided to include this API directly in JUnit. It's an extensible and readable syntax, and it enables new features, like [assumptions][] and [theories][]. [assumptions]: #assumptions [theories]: #theories Some notes: - The old assert methods are never, ever, going away. Developers may continue using the old `assertEquals`, `assertTrue`, and so on. - The second parameter of an `assertThat` statement is a `Matcher`. We include the Matchers we want as static imports, like this: import static org.hamcrest.CoreMatchers.is; or: import static org.hamcrest.CoreMatchers.*; - Manually importing `Matcher` methods can be frustrating. [Eclipse 3.3][] includes the ability to define "Favorite" classes to import static methods from, which makes it easier (Search for "Favorites" in the Preferences dialog). We expect that support for static imports will improve in all Java IDEs in the future. [Eclipse 3.3]: http://www.eclipse.org/downloads/ - To allow compatibility with a wide variety of possible matchers, we have decided to include the classes from hamcrest-core, from the [Hamcrest][] project. This is the first time that third-party classes have been included in JUnit. [Hamcrest]: http://code.google.com/p/hamcrest/ - JUnit currently ships with a few matchers, defined in `org.hamcrest.CoreMatchers` and `org.junit.matchers.JUnitMatchers`. To use many, many more, consider downloading the [full hamcrest package][]. [full hamcrest package]: http://hamcrest.googlecode.com/files/hamcrest-all-1.1.jar - JUnit contains special support for comparing string and array values, giving specific information on how they differ. This is not yet available using the `assertThat` syntax, but we hope to bring the two assert methods into closer alignment in future releases. <a name="assumptions" /> ### Assumptions ### Ideally, the developer writing a test has control of all of the forces that might cause a test to fail. If this isn't immediately possible, making dependencies explicit can often improve a design. For example, if a test fails when run in a different locale than the developer intended, it can be fixed by explicitly passing a locale to the domain code. However, sometimes this is not desirable or possible. It's good to be able to run a test against the code as it is currently written, implicit assumptions and all, or to write a test that exposes a known bug. For these situations, JUnit now includes the ability to express "assumptions": import static org.junit.Assume.* @Test public void filenameIncludesUsername() { assumeThat(File.separatorChar, is('/')); assertThat(new User("optimus").configFileName(), is("configfiles/optimus.cfg")); } @Test public void correctBehaviorWhenFilenameIsNull() { assumeTrue(bugFixed("13356")); // bugFixed is not included in JUnit assertThat(parse(null), is(new NullDocument())); } With this release, a failed assumption will lead to the test being marked as passing, regardless of what the code below the assumption may assert. In the future, this may change, and a failed assumption may lead to the test being ignored: however, third-party runners do not currently allow this option. We have included `assumeTrue` for convenience, but thanks to the inclusion of Hamcrest, we do not need to create `assumeEquals`, `assumeSame`, and other analogues to the `assert*` methods. All of those functionalities are subsumed in `assumeThat`, with the appropriate matcher. A failing assumption in a `@Before` or `@BeforeClass` method will have the same effect as a failing assumption in each `@Test` method of the class. <a name="theories" /> ### Theories ### More flexible and expressive assertions, combined with the ability to state assumptions clearly, lead to a new kind of statement of intent, which we call a "Theory". A test captures the intended behavior in one particular scenario. A theory captures some aspect of the intended behavior in possibly infinite numbers of potential scenarios. For example: @RunWith(Theories.class) public class UserTest { @DataPoint public static String GOOD_USERNAME = "optimus"; @DataPoint public static String USERNAME_WITH_SLASH = "optimus/prime"; @Theory public void filenameIncludesUsername(String username) { assumeThat(username, not(containsString("/"))); assertThat(new User(username).configFileName(), containsString(username)); } } This makes it clear that the user's filename should be included in the config file name, only if it doesn't contain a slash. Another test or theory might define what happens when a username does contain a slash. `UserTest` will attempt to run `filenameIncludesUsername` on every compatible `DataPoint` defined in the class. If any of the assumptions fail, the data point is silently ignored. If all of the assumptions pass, but an assertion fails, the test fails. The support for Theories has been absorbed from the [Popper][] project, and [more complete documentation][popper-docs] can be found there. [Popper]: http://popper.tigris.org [popper-docs]: http://popper.tigris.org/tutorial.html Defining general statements in this way can jog the developer's memory about other potential data points and tests, also allows [automated tools][junit-factory] to [search][my-blog] for new, unexpected data points that expose bugs. [junit-factory]: http://www.junitfactory.org [my-blog]: http://shareandenjoy.saff.net/2007/04/popper-and-junitfactory.html ### Other changes ### This release contains other bug fixes and new features. Among them: - Annotated descriptions Runner UIs, Filters, and Sorters operate on Descriptions of test methods and test classes. These Descriptions now include the annotations on the original Java source element, allowing for richer display of test results,