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[英]Why doesn't JUnit's ExpectedException lead to unpredictable state?
[英]Unable to expect multiple exceptions with JUnit's ExpectedException
我正在编写测试以验证我的方法的合同,例如,参数不能为null
, int
参数必须为正,等等。当违反合同时,抛出的异常类型将反映其失败的原因,例如NullPointerException
或IllegalArgumentException
。 有时我不在乎这两个中的哪一个被抛出,仅是其中之一被抛出。 (是的,我应该测试确切的异常类型,但是请忍受...)
我可以使用JUnit的@Test(expected = RuntimeException.class)
(因为RuntimeException
是IAE
和NPE
的最接近的公共父级),但是由于测试中的方法可能会抛出其他RuntimeException
,因此这过于笼统。
相反,我试图使用JUnit的ExpectedExceptions
类。
这是一个完整的示例:
import org.hamcrest.CoreMatchers;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.ExpectedException;
import static org.hamcrest.CoreMatchers.anyOf;
public class ParameterViolationTest {
private Target target = new Target();
@Rule
public ExpectedException expected = ExpectedException.none();
@Test
public void parameterViolation() {
expected.expect(anyOf(
CoreMatchers.<Class<? extends Exception>>
equalTo(NullPointerException.class),
CoreMatchers.<Class<? extends Exception>>
equalTo(IllegalArgumentException.class)));
// Null parameter violates contract, throws some exception.
target.methodUnderTest(null);
}
private static class Target {
public void methodUnderTest(Object o) {
if (o == null) {
// throw new IllegalArgumentException();
throw new NullPointerException();
}
}
}
}
我希望该测试能够通过,但是失败了:
java.lang.AssertionError:
Expected: (<class java.lang.NullPointerException> or <class java.lang.IllegalArgumentException>)
but: was <java.lang.NullPointerException>
Stacktrace was: java.lang.NullPointerException
at ParameterViolationTest$Target.methodUnderTest(ParameterViolationTest.java:35)
at ParameterViolationTest.parameterViolation(ParameterViolationTest.java:25)
< internal calls... >
at org.junit.rules.ExpectedException$ExpectedExceptionStatement.evaluate(ExpectedException.java:168)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
< internal calls... >
java.lang.AssertionError:
Expected: (<class java.lang.NullPointerException> or <class java.lang.IllegalArgumentException>)
but: was <java.lang.NullPointerException>
Stacktrace was: java.lang.NullPointerException
at ParameterViolationTest$Target.methodUnderTest(ParameterViolationTest.java:35)
at ParameterViolationTest.parameterViolation(ParameterViolationTest.java:25)
< internal calls... >
at org.junit.rules.ExpectedException$ExpectedExceptionStatement.evaluate(ExpectedException.java:168)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
< internal calls... >
at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
at org.junit.Assert.assertThat(Assert.java:865)
at org.junit.Assert.assertThat(Assert.java:832)
at org.junit.rules.ExpectedException.handleException(ExpectedException.java:198)
at org.junit.rules.ExpectedException.access$500(ExpectedException.java:85)
at org.junit.rules.ExpectedException$ExpectedExceptionStatement.evaluate(ExpectedException.java:177)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
< internal calls... >
这里发生了什么?
你必须使用Matchers.instanceOf
代替CoreMatchers.equalTo
,因为你比较的情况下XXXException
。
expected.expect(anyOf(
instanceOf(NullPointerException.class),
instanceOf(IllegalArgumentException.class)));
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