在我以前的文章中，我展示了有關JavaBeans單元測試的一些技巧。 在此博客文章中，我將提供有關單元測試某些相當常見的Java代碼的另外兩個技巧，即實用程序類和Log4J日志記錄語句 。

測試實用程序類

如果您的實用程序類遵循與我傾向于編寫的相同的基本設計，則它們由帶有私有構造函數和所有靜態方法的最終類組成。

實用類測試儀

package it.jdev.example;import static org.junit.Assert.*;import java.lang.reflect.*;import org.junit.Test;/*** Tests that a utility class is final, contains one private constructor, and* all methods are static.*/ public final class UtilityClassTester {private UtilityClassTester() {super();}/*** Verifies that a utility class is well defined.* * @param clazz* @throws Exception*/@Testpublic static void test(final Class<?> clazz) throws Exception {// Utility classes must be final.assertTrue("Class must be final.", Modifier.isFinal(clazz.getModifiers()));// Only one constructor is allowed and it has to be private.assertTrue("Only one constructor is allowed.", clazz.getDeclaredConstructors().length == 1);final Constructor<?> constructor = clazz.getDeclaredConstructor();assertFalse("Constructor must be private.", constructor.isAccessible());assertTrue("Constructor must be private.", Modifier.isPrivate(constructor.getModifiers()));// All methods must be static.for (final Method method : clazz.getMethods()) {if (!Modifier.isStatic(method.getModifiers()) && method.getDeclaringClass().equals(clazz)) {fail("Non-static method found: " + method + ".");}}}}

該UtilityClassTester本身也遵循上面提到的實用程序類約束，因此有什么更好的方法通過使用它來測試自身來證明其用途：

UtilityClassTester的測試用例

package it.jdev.example;import org.junit.Test;public class UtilityClassTesterTest {@Testpublic void test() throws Exception {UtilityClassTester.test(UtilityClassTester.class);}}

測試Log4J記錄事件

調用聲明異常的方法時，您將重新聲明該異常，或者嘗試在try-catch塊中對其進行處理。 在后一種情況下，至少要做的是記錄捕獲的異常。 下面是一個非常簡單的示例：

MyService示例

package it.jdev.example;import java.lang.invoke.MethodHandles;import org.apache.log4j.Logger; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service;@Service public class MyService {private static final Logger LOGGER = Logger.getLogger(MethodHandles.Lookup.class);@Autowiredprivate MyRepository myRepository;public void doSomethingUseful() {try {myRepository.doSomethingVeryUseful();} catch (SomeException e) {LOGGER.error("Some very informative error logging.", e);}}}

當然，您將需要測試是否正確記錄了異常。 遵循以下內容：

MyService日志記錄事件的測試用例

package it.jdev.example;import static org.junit.Assert.*;import org.apache.log4j.spi.LoggingEvent; import org.junit.*; import org.mockito.*;public class MyServiceTest {@Mockprivate MyRepository myRepository;@InjectMocksprivate MyService myService = new MyService();@Beforepublic void setup() {MockitoAnnotations.initMocks(this);}@Testpublic void thatSomeExceptionIsLogged() throws Exception {TestAppender testAppender = new TestAppender();Mockito.doThrow(SomeException.class).when(myRepository).doSomethingVeryUseful();myService.doSomethingUseful();assertTrue(testAppender.getEvents().size() == 1);final LoggingEvent loggingEvent = testAppender.getEvents().get(0);assertEquals("Some very informative error logging.", loggingEvent.getMessage().toString());}}

但是，如何實現這一目標呢？ 事實證明，將新的LogAppender添加到Log4J RootLogger非常容易。

用于Log4J的TestAppender

package it.jdev.example;import java.util.*;import org.apache.log4j.*; import org.apache.log4j.spi.*;/*** Utility for testing Log4j logging events.* <p>* Usage:<br />* <code>* TestAppender testAppender = new TestAppender();<br />* classUnderTest.methodThatWillLog();<br /><br />* LoggingEvent loggingEvent = testAppender.getEvents().get(0);<br /><br />* assertEquals()...<br /><br />* </code>*/ public class TestAppender extends AppenderSkeleton {private final List<LoggingEvent> events = new ArrayList<LoggingEvent>();public TestAppender() {this(Level.ERROR);}public TestAppender(final Level level) {super();Logger.getRootLogger().addAppender(this);this.addFilter(new LogLevelFilter(level));}@Overrideprotected void append(final LoggingEvent event) {events.add(event);}@Overridepublic void close() {}@Overridepublic boolean requiresLayout() {return false;}public List<LoggingEvent> getEvents() {return events;}/*** Filter that decides whether to accept or deny a logging event based on* the logging level.*/protected class LogLevelFilter extends Filter {private final Level level;public LogLevelFilter(final Level level) {super();this.level = level;}@Overridepublic int decide(final LoggingEvent event) {if (event.getLevel().isGreaterOrEqual(level)) {return ACCEPT;} else {return DENY;}}}}

翻譯自: https://www.javacodegeeks.com/2014/09/some-more-unit-test-tips.html

總結

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