Java：使用 Junit 3 进行异常测试

Java: Exception testing with Junit 3

提问by Mobidoy

I would like to write a test for IndexOutOfBoundsException. Keep in mind that we are supposed to use JUnit 3.

我想为IndexOutOfBoundsException. 请记住，我们应该使用 JUnit 3。

My code:

我的代码：

public boolean ajouter(int indice, T element) {
    if (indice < 0 || indice > (maListe.size() - 1)) {
        throw new IndexOutOfBoundsException();
    } else if (element != null && !maListe.contains(element)) {
        maListe.set(indice, element);
        return true;
    }
}

After some research, I found that you can do this with JUnit 4 using @Test(expected = IndexOutOfBoundsException.class)but no where did I find how to do this in JUnit 3.

经过一些研究，我发现您可以使用 JUnit 4 执行此操作，@Test(expected = IndexOutOfBoundsException.class)但我在 JUnit 3 中找不到如何执行此操作的方法。

How can I test this using JUnit 3?

如何使用 JUnit 3 对此进行测试？

回答by Aaron Digulla

Testing exceptions in JUnit 3 uses this pattern:

JUnit 3 中的测试异常使用这种模式：

try {
     ... code that should throw an exception ...

     fail( "Missing exception" );
} catch( IndexOutOfBoundsException e ) {
     assertEquals( "Expected message", e.getMessage() ); // Optionally make sure you get the correct message, too
}

The fail()makes sure you get an error if the code doesn't throw an exception.

fail()如果代码没有抛出异常，这将确保你得到一个错误。

I use this pattern in JUnit 4 as well since I usually want to make sure the correct values are visible in the exception message and @Testcan't do that.

我也在 JUnit 4 中使用这种模式，因为我通常想确保正确的值在异常消息中可见，但我@Test不能这样做。

回答by Jon Skeet

Basically, you need to call your method and fail if it doesn'tthrow the right exception - or if it throws anything else:

基本上，你需要调用你的方法，如果它没有抛出正确的异常，或者它抛出其他任何东西，就会失败：

try {
  subject.ajouter(10, "foo");
  fail("Expected exception");
} catch (IndexOutOfBoundException expect) {
  // We should get here. You may assert things about the exception, if you want.
}

回答by Janoz

A simple solution is to add a try catch to the unittest and let the test fail when the exception isn't thrown

一个简单的解决方案是在单元测试中添加一个try catch，并在没有抛出异常时让测试失败

public void testAjouterFail() {
  try {
    ajouter(-1,null);
    JUnit.fail();
  catch (IndexOutOfBoundException()) {
    //success
  }
}

回答by COMCY2002

One thing you can do is use a boolean to run the test to completion and then you can use assert to validate the exception was thrown:

您可以做的一件事是使用布尔值来运行测试直至完成，然后您可以使用 assert 来验证抛出的异常：

boolean passed = false;
try
{
    //the line that throws exception
    //i.e. illegal argument exception
    //if user tries to set the property to null:
    myObject.setProperty(null);
}
catch (IllegalArgumentException iaex)
{
    passed = true;
}
assertTrue("The blah blah blah exception was not thrown as expected"
              , passed);

By using this test, your test will never fail to execute and you can validate that a specific exception type is thrown.

通过使用此测试，您的测试将永远不会执行失败，并且您可以验证是否抛出了特定的异常类型。

回答by karmakaze

Extending @Aaron's solution with some (static import) syntactic sugar allows writing:

使用一些（静态导入）语法糖扩展@Aaron 的解决方案允许编写：

    expected(MyException.class,
        new Testable() {
            public void test() {
            ... do thing that's supposed to throw MyException ...
            }
        });

Testableis like a Runnable which uses test() signature throwing Throwable.

Testable就像一个 Runnable，它使用 test() 签名抛出 Throwable。

public class TestHelper {
    public static void expected(Class<? extends Throwable> expectedClass, Testable testable) {
        try {
            testable.test();
            fail("Expected "+ expectedClass.getCanonicalName() +" not thrown.");
        } catch (Throwable actual) {
            assertEquals("Expected "+ expectedClass.getCanonicalName() +" to be thrown.", expectedClass, actual.getClass());
        }
    }

    interface Testable {
        public void test() throws Throwable;
    }
}

You could add checking of the exception message as required.

您可以根据需要添加对异常消息的检查。

回答by Raedwald

In your test method, call ajouter()inside a try..catchblock, giving a value of indicethat should cause the exception to be thrown, with

在您的测试方法中，ajouter()在try..catch块内调用，给出一个值indice应该会导致抛出异常，用

• a catchclause that catches IndexOutOfBoundsException: in that case return from your test method and thus indicate a pass.
• a second catchclause that catches Throwable: in that case declare a failure (call fail()), because the wrong kind of exception was thrown
• after the try..catchdeclare a failure (call fail()), because no exception was thrown.

• 一个catch捕获IndexOutOfBoundsException: 在这种情况下从您的测试方法返回的子句，从而表明通过。
• catch捕获的第二个子句Throwable：在这种情况下声明失败（调用fail()），因为抛出了错误类型的异常
• 在try..catch声明失败（调用fail()）之后，因为没有抛出异常。