使用junit @Rule、expectCause()和hamcrest匹配器
使用junit @Rule、expectCause()和hamcrest匹配器
提问于 2014-03-12 16:50:45
我有个测试：
@Rule
public ExpectedException thrown = ExpectedException.none();
...
@Test
public void testMethod()
{
final String error = "error message";
Throwable expectedCause = new IllegalStateException(error);
thrown.expectCause(org.hamcrest.Matchers.<Throwable>equalTo(expectedCause));
someServiceThatTrowsException.foo();
}当通过mvn运行测试方法时，我得到了错误：
org.junit.rules.ExpectedException.expectCause(Lorg/hamcrest/Matcher;)V：
java.lang.NoSuchMethodError
测试编译正常。
请帮帮我，不明白如何测试异常的原因？
回答 10
Stack Overflow用户
发布于 2014-03-12 17:03:27
这样试试：
@Rule public ExpectedException thrown = ExpectedException.none();
@Test public void testMethod() throws Throwable {
final String error = "error message";
Throwable expectedCause = new IllegalStateException(error);
thrown.expectCause(IsEqual.equalTo(expectedCause));
throw new RuntimeException(expectedCause);
}如有必要，请考虑不要通过等于而是通过IsInstanceOf和/或比较异常消息来检查原因。通过相等比较原因也会检查堆栈跟踪，这可能比您想要测试/检查的更多。例如，如下所示：
@Rule public ExpectedException thrown = ExpectedException.none();
@Test public void testMethod() throws Throwable {
final String error = "error message";
thrown.expectCause(IsInstanceOf.<Throwable>instanceOf(IllegalStateException.class));
thrown.expectMessage(error);
throw new RuntimeException(new IllegalStateException(error));
}Stack Overflow用户
发布于 2016-08-30 15:49:05
简单介绍一下静态导入，同时检查类和原因异常的消息：
import static org.hamcrest.Matchers.allOf;
import static org.hamcrest.Matchers.hasProperty;
import static org.hamcrest.Matchers.instanceOf;
import static org.hamcrest.Matchers.is;
import static org.junit.Assert.assertThat;
@Test
public void testThatThrowsNiceExceptionWithCauseAndMessages(){
expectedException.expect(RuntimeException.class );
expectedException.expectMessage("Exception message");
expectedException.expectCause(allOf(instanceOf(IllegalStateException.class),
hasProperty("message", is("Cause message"))) );
throw new RuntimeException("Exception message", new IllegalStateException("Cause message"));
}您甚至可以使用hasProperty匹配器来断言嵌套的原因或测试"getLocalizedMessage“方法。
Stack Overflow用户
发布于 2014-09-19 19:12:54
您可以使用此处描述的自定义匹配器(http://www.javacodegeeks.com/2014/03/junit-expectedexception-rule-beyond-basics.html)来测试异常的原因。
自定义匹配器
private static class CauseMatcher extends TypeSafeMatcher<Throwable> {
private final Class<? extends Throwable> type;
private final String expectedMessage;
public CauseMatcher(Class<? extends Throwable> type, String expectedMessage) {
this.type = type;
this.expectedMessage = expectedMessage;
}
@Override
protected boolean matchesSafely(Throwable item) {
return item.getClass().isAssignableFrom(type)
&& item.getMessage().contains(expectedMessage);
}
@Override
public void describeTo(Description description) {
description.appendText("expects type ")
.appendValue(type)
.appendText(" and a message ")
.appendValue(expectedMessage);
}
}测试用例
@Rule
public ExpectedException thrown = ExpectedException.none();
@Test
public void verifiesCauseTypeAndAMessage() {
thrown.expect(RuntimeException.class);
thrown.expectCause(new CauseMatcher(IllegalStateException.class, "Illegal state"));
throw new RuntimeException("Runtime exception occurred",
new IllegalStateException("Illegal state"));
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/22346275
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