JUnit:可能'期望'包装异常？

您可以将测试代码包装在try/catch块中,捕获抛出的异常,检查内部原因,log/assert/whatever,然后重新抛出异常(如果需要).

如果您使用的是最新版本的JUnit,则可以扩展默认测试运行器以便为您处理(无需将每个方法包装在try/catch块中)

ExtendedTestRunner.java - 新的测试运行器:

public class ExtendedTestRunner extends BlockJUnit4ClassRunner
{
    public ExtendedTestRunner( Class clazz )
        throws InitializationError
    {
        super( clazz );
    }

    @Override
    protected Statement possiblyExpectingExceptions( FrameworkMethod method,
                                                     Object test,
                                                     Statement next )
    {
        ExtendedTest annotation = method.getAnnotation( ExtendedTest.class );
        return expectsCauseException( annotation ) ?
                new ExpectCauseException( next, getExpectedCauseException( annotation ) ) :
                super.possiblyExpectingExceptions( method, test, next );
    }

    @Override
    protected List computeTestMethods()
    {
        Set testMethods = new HashSet( super.computeTestMethods() );
        testMethods.addAll( getTestClass().getAnnotatedMethods( ExtendedTest.class ) );
        return testMethods;
    }

    @Override
    protected void validateTestMethods( List errors )
    {
        super.validateTestMethods( errors );
        validatePublicVoidNoArgMethods( ExtendedTest.class, false, errors );
    }

    private Class getExpectedCauseException( ExtendedTest annotation )
    {
        if (annotation == null || annotation.expectedCause() == ExtendedTest.None.class)
            return null;
        else
            return annotation.expectedCause();
    }

    private boolean expectsCauseException( ExtendedTest annotation) {
        return getExpectedCauseException(annotation) != null;
    }

}

ExtendedTest.java - 用于标记测试方法的注释:

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface ExtendedTest
{

    /**
     * Default empty exception
     */
    static class None extends Throwable {
        private static final long serialVersionUID= 1L;
        private None() {
        }
    }

    Class expectedCause() default None.class;
}

ExpectCauseException.java - 新的JUnit语句:

public class ExpectCauseException extends Statement
{
    private Statement fNext;
    private final Class fExpected;

    public ExpectCauseException( Statement next, Class expected )
    {
        fNext= next;
        fExpected= expected;
    }

    @Override
    public void evaluate() throws Exception
    {
        boolean complete = false;
        try {
            fNext.evaluate();
            complete = true;
        } catch (Throwable e) {
            if ( e.getCause() == null || !fExpected.isAssignableFrom( e.getCause().getClass() ) )
            {
                String message = "Unexpected exception cause, expected<"
                            + fExpected.getName() + "> but was<"
                            + ( e.getCause() == null ? "none" : e.getCause().getClass().getName() ) + ">";
                throw new Exception(message, e);
            }
        }
        if (complete)
            throw new AssertionError( "Expected exception cause: "
                    + fExpected.getName());
    }
}

用法:

@RunWith( ExtendedTestRunner.class )
public class MyTests
{
    @ExtendedTest( expectedCause = MyException.class )
    public void someMethod()
    {
        throw new RuntimeException( new MyException() );
    }
}

您可以随时手动执行此操作:

@Test
public void someMethod() {
    try{
        ... all your code
    } catch (Exception e){
        // check your nested clauses
        if(e.getCause() instanceof FooException){
            // pass
        } else {
            Assert.fail("unexpected exception");
        }
    }

您可以为异常创建匹配器.当你正在使用其他的测试运行像这样的作品即使的Arquillian的@RunWith(Arquillian.class),所以你不能使用@RunWith(ExtendedTestRunner.class)方法上面建议.

这是一个简单的例子:

public class ExceptionMatcher extends BaseMatcher