我有一些正在测试的代码，它调用Java记录器来报告其状态。 在JUnit测试代码中，我想验证在这个日志记录器中创建了正确的日志条目。大致如下:
methodUnderTest(bool x){
if(x)
logger.info("x happened")
}
@Test tester(){
// perhaps setup a logger first.
methodUnderTest(true);
assertXXXXXX(loggedLevel(),Level.INFO);
}
我认为这可以用一个经过特别调整的记录器(或处理程序或格式化程序)来完成，但我更愿意重用现有的解决方案。(而且，老实说，我不清楚如何从记录器获得logRecord，但假设这是可能的。)
当前回答
受到@RonaldBlaschke的解决方案的启发，我想到了这个:
public class Log4JTester extends ExternalResource {
TestAppender appender;
@Override
protected void before() {
appender = new TestAppender();
final Logger rootLogger = Logger.getRootLogger();
rootLogger.addAppender(appender);
}
@Override
protected void after() {
final Logger rootLogger = Logger.getRootLogger();
rootLogger.removeAppender(appender);
}
public void assertLogged(Matcher<String> matcher) {
for(LoggingEvent event : appender.events) {
if(matcher.matches(event.getMessage())) {
return;
}
}
fail("No event matches " + matcher);
}
private static class TestAppender extends AppenderSkeleton {
List<LoggingEvent> events = new ArrayList<LoggingEvent>();
@Override
protected void append(LoggingEvent event) {
events.add(event);
}
@Override
public void close() {
}
@Override
public boolean requiresLayout() {
return false;
}
}
}
．.． 这允许你做:
@Rule public Log4JTester logTest = new Log4JTester();
@Test
public void testFoo() {
user.setStatus(Status.PREMIUM);
logTest.assertLogged(
stringContains("Note added to account: premium customer"));
}
你也许可以用更聪明的方式来使用hamcrest，但我就讲到这里。
其他回答
这里有一个很好的和优雅的方法来解决这个问题: https://www.baeldung.com/junit-asserting-logs
这是我为logback所做的。
我创建了一个TestAppender类:
public class TestAppender extends AppenderBase<ILoggingEvent> {
private Stack<ILoggingEvent> events = new Stack<ILoggingEvent>();
@Override
protected void append(ILoggingEvent event) {
events.add(event);
}
public void clear() {
events.clear();
}
public ILoggingEvent getLastEvent() {
return events.pop();
}
}
然后在我的testng单元测试类的父类中创建了一个方法:
protected TestAppender testAppender;
@BeforeClass
public void setupLogsForTesting() {
Logger root = (Logger)LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);
testAppender = (TestAppender)root.getAppender("TEST");
if (testAppender != null) {
testAppender.clear();
}
}
我在src/test/resources中定义了一个logback-test.xml文件，并添加了一个测试appender:
<appender name="TEST" class="com.intuit.icn.TestAppender">
<encoder>
<pattern>%m%n</pattern>
</encoder>
</appender>
并将这个appender添加到根appender:
<root>
<level value="error" />
<appender-ref ref="STDOUT" />
<appender-ref ref="TEST" />
</root>
现在，在从父测试类扩展而来的测试类中，我可以获得appender并记录最后一条消息，并验证消息、级别和throwable。
ILoggingEvent lastEvent = testAppender.getLastEvent();
assertEquals(lastEvent.getMessage(), "...");
assertEquals(lastEvent.getLevel(), Level.WARN);
assertEquals(lastEvent.getThrowableProxy().getMessage(), "...");
受到@RonaldBlaschke的解决方案的启发，我想到了这个:
public class Log4JTester extends ExternalResource {
TestAppender appender;
@Override
protected void before() {
appender = new TestAppender();
final Logger rootLogger = Logger.getRootLogger();
rootLogger.addAppender(appender);
}
@Override
protected void after() {
final Logger rootLogger = Logger.getRootLogger();
rootLogger.removeAppender(appender);
}
public void assertLogged(Matcher<String> matcher) {
for(LoggingEvent event : appender.events) {
if(matcher.matches(event.getMessage())) {
return;
}
}
fail("No event matches " + matcher);
}
private static class TestAppender extends AppenderSkeleton {
List<LoggingEvent> events = new ArrayList<LoggingEvent>();
@Override
protected void append(LoggingEvent event) {
events.add(event);
}
@Override
public void close() {
}
@Override
public boolean requiresLayout() {
return false;
}
}
}
．.． 这允许你做:
@Rule public Log4JTester logTest = new Log4JTester();
@Test
public void testFoo() {
user.setStatus(Status.PREMIUM);
logTest.assertLogged(
stringContains("Note added to account: premium customer"));
}
你也许可以用更聪明的方式来使用hamcrest，但我就讲到这里。
简单的方法
@ExtendWith(OutputCaptureExtension.class)
class MyTestClass {
@Test
void my_test_method(CapturedOutput output) {
assertThat(output).contains("my test log.");
}
}
另一个值得提及的想法是创建一个CDI生成器来注入记录器，这样模拟就变得容易了，尽管这是一个较老的主题。(而且它还提供了不必再声明“整个logger语句”的优势，但这已经跑题了)
例子:
创建要注入的记录器:
public class CdiResources {
@Produces @LoggerType
public Logger createLogger(final InjectionPoint ip) {
return Logger.getLogger(ip.getMember().getDeclaringClass());
}
}
限定符:
@Qualifier
@Retention(RetentionPolicy.RUNTIME)
@Target({TYPE, METHOD, FIELD, PARAMETER})
public @interface LoggerType {
}
在生产代码中使用记录器:
public class ProductionCode {
@Inject
@LoggerType
private Logger logger;
public void logSomething() {
logger.info("something");
}
}
在测试代码中测试记录器(给出一个easyMock示例):
@TestSubject
private ProductionCode productionCode = new ProductionCode();
@Mock
private Logger logger;
@Test
public void testTheLogger() {
logger.info("something");
replayAll();
productionCode.logSomething();
}
