在进阶二中,我们介绍了@Rule
的两个用法,对异常进行检查和对超时时间的设定。其实,Rule还有很多用途,本文将做进一步介绍。
Rule的应用
Rule将在框架的很多方面提供解决方案。下面一一举例:
-
TemporaryFolder
TemporaryFolder
作为Rule,可以运行在测试过程中创建临时文件或者临时目录,当测试结束后,框架会自动删除。见实例:
public static class HasTempFolder { @Rule public TemporaryFolder folder = new TemporaryFolder(); @Test public void testUsingTempFolder() throws IOException { File createdFile = folder.newFile("myfile.txt"); File createdFolder = folder.newFolder("subfolder"); // ... } }
TemporaryFolder#newFolder(String... folderNames)
可以根据输入的参数创建目录。如果是多级目录,可以递归创建。TemporaryFolder#newFile()
可以创建一个随机名字的临时文件;TemporaryFolder##newFolder()
可以创建一个随机名字的临时目录。
-
ExternalResource
ExternalResource
可以设置测试前后需要做的事情(比如:文件、socket、服务、数据库的连接与关闭)。这个我们在之前的进阶二中稍有提及。见实例:
public static class UsesExternalResource { Server myServer = new Server(); @Rule public ExternalResource resource = new ExternalResource() { @Override protected void before() throws Throwable { myServer.connect(); }; @Override protected void after() { myServer.disconnect(); }; }; @Test public void testFoo() { new Client().run(myServer); } }
ExternalResource#before
会在每个测试之前处理;#after
会在每个测试之后处理;- 关于
ExternalResource
与@Before
已经@After
等标记步骤的执行顺序,我们会在本文后面部分介绍。
-
ErrorCollector
ErrorCollector
这个Rule,在出现一个错误后,还可以让测试继续进行下去。他提供三个方法:
checkThat(final T value, Matcher<T> matcher) checkSucceeds(Callable<Object> callable) addError(Throwable error)
前面两个是用来处理断言的,最后一个是添加错误至错误列表中。
看下面例子:
package mytest; import static org.hamcrest.CoreMatchers.is; import static org.junit.Assert.assertThat; import java.util.concurrent.Callable; import org.junit.Rule; import org.junit.Test; import org.junit.rules.ErrorCollector; public class JUnitCoreErrorControllerRuleTest { private final int multiplesOf2[] = { 0, 2, 4, 7, 8, 11, 12 }; @Rule public ErrorCollector errorCollector = new ErrorCollector(); /* * 下面这个测试,会报告两个failures。这一点和下面的checkSucceeds测试不同 */ @Test public void testMultiplesOf2() { int multiple = 0; for (int multipleOf2 : multiplesOf2) { // Will count the number of issues in this list // - 3*2 = 6 not 7, 5*2 = 10 not 11 : 2 Failures errorCollector.checkThat(2 * multiple, is(multipleOf2)); multiple++; } } /* * 下面代码中有两个断言会失败,但每次运行JUnit框架只会报告一个。这一点和上面的checkThat测试不同,可以对比一下。 */ @Test public void testCallableMultiples() { errorCollector.checkSucceeds(new Callable<Object>() { public Object call() throws Exception { assertThat(2 * 2, is(5)); assertThat(2 * 3, is(6)); assertThat(2 * 4, is(8)); assertThat(2 * 5, is(9)); return null; } }); } /* * 下面运行时,会报告2个错误 */ @Test public void testAddingAnError() { assertThat(2 * 2, is(4)); errorCollector.addError(new Throwable("Error Collector added an error")); assertThat(2 * 3, is(6)); errorCollector.addError(new Throwable( "Error Collector added a second error")); } }
运行结果,类似下面:
Failed tests: testCallableMultiples(mytest.JUnitCoreErrorControllerRuleTest):Expected: is <5> but: was <4>
Expected: is <7>
but: was <6>
Expected: is <11>
but: was <10>
Tests in error:
testAddingAnError(tangzhi.mytest.JUnitCoreErrorControllerRuleTest): Error Collector added an error
从这个例子,可以看出:
* `ErrorCollector#checkThat` 会报告测试中的每一个failures
* `ErrorCollector#checkSucceeds` 只会检查是否成功,如果不成功,只报告第一个导致不成功的failure
* `ErrorCollector#addError` 是添加一个错误(error)。
-
Verifier
如果,你想在每个测试之后,甚至是在
@After
之后,想检查些什么,就可以使用Verifier
这个Rule.看例子:
private static String sequence; public static class UsesVerifier { @Rule public Verifier collector = new Verifier() { @Override protected void verify() { sequence += " verify "; } }; @Test public void example() { sequence += "test"; } @Test public void example2() { sequence += "test2"; } @After public void after() { sequence += " after"; } } @Test public void verifierRunsAfterTest() { sequence = ""; assertThat(testResult(UsesVerifier.class), isSuccessful()); assertEquals("test after verify test2 after verify ", sequence); }
从上面例子可以看出:
Verifier#verify
针对每个测试都会运行一次,并且运行在@After
步骤之后。需要说明:如果某测试出现失败(fail),那么这个测试之后就不会做
verify
,这一点,可以结合下面的例子看出。 -
TestWatcher
对测试的每个步骤进行监控。
看例子:
package tangzhi.mytest; import static org.junit.Assert.*; import static org.hamcrest.CoreMatchers.*; import org.junit.After; import org.junit.Rule; import org.junit.Test; import org.junit.rules.TestRule; import org.junit.rules.TestWatcher; import org.junit.rules.Verifier; import org.junit.runner.Description; import org.junit.runners.model.Statement; public class WatchmanTest { private static String watchedLog; @Rule public TestRule watchman = new TestWatcher() { @Override public Statement apply(Statement base, Description description) { Statement s = super.apply(base, description); watchedLog=""; System.out.println("watch apply."); return s; } @Override protected void succeeded(Description description) { watchedLog += description.getDisplayName() + " " + "success!"; System.out.println("watch succeed:"+watchedLog); } @Override protected void failed(Throwable e, Description description) { watchedLog += description.getDisplayName() + " " + e.getClass().getSimpleName(); System.out.println("watch failed:"+watchedLog); } @Override protected void starting(Description description) { super.starting(description); System.out.println("watch starting."); } @Override protected void finished(Description description) { super.finished(description); System.out.println("watch finished."); } }; @Rule public Verifier collector = new Verifier() { @Override protected void verify() { System.out.println("@Verify:"+watchedLog); } }; @Test public void fails() { System.out.println("in fails"); assertThat("ssss", is("sss")); } @Test public void succeeds() { System.out.println("in succeeds"); } @After public void after() { System.out.println("@After"); } }
运行后,日志如下:
watch apply. watch starting. in succeeds @After watch succeed:succeeds(tangzhi.mytest.WatchmanTest) success! watch finished. @Verify:succeeds(tangzhi.mytest.WatchmanTest) success! watch apply. watch starting. in fails @After watch failed:fails(tangzhi.mytest.WatchmanTest) AssertionError watch finished.
-
TestName
TestName
可以获取当前测试方法的名字。看例子:
public class NameRuleTest { @Rule public TestName name = new TestName(); @Test public void testA() { assertEquals("testA", name.getMethodName()); } @Test public void testB() { assertEquals("testB", name.getMethodName()); } }
如果,是在参数化测试(Parameterized)中,使用了
@Parameters
,那么其name
属性定义的方法名也将会被TestName#getMethodName
获取。 -
Timeout
这个我们在前面介绍过,可以设置某个测试类,所有测试方法的超时时间。详见进阶二。
-
ExpectedException
这个也在进阶二中有介绍。
-
ClassRule
注释
@ClassRule
是类级别的,而不是方法级别的。见下面例子:
@RunWith(Suite.class) @SuiteClasses({A.class, B.class, C.class}) public class UsesExternalResource { public static Server myServer= new Server(); @ClassRule public static ExternalResource resource= new ExternalResource() { @Override protected void before() throws Throwable { myServer.connect(); }; @Override protected void after() { myServer.disconnect(); }; }; }
在Suite所打包的几个类测试前后,会执行一遍
ClassRule
。 -
RuleChain
public static class UseRuleChain {
@Rule
public TestRule chain= RuleChain
.outerRule(new LoggingRule("outer rule")
.around(new LoggingRule("middle rule")
.around(new LoggingRule("inner rule");
@Test
public void example() {
assertTrue(true);
}
}
starting middle rule
starting inner rule
finished inner rule
finished middle rule
finished outer rule