問題描述

我需要模擬一個測試場景，在該場景中我調(diào)用 String 對象的 getBytes() 方法并得到 UnsupportedEncodingException.

I need to simulate a test scenario in which I call the getBytes() method of a String object and I get an UnsupportedEncodingException.

我已嘗試使用以下代碼來實(shí)現(xiàn):

I have tried to achieve that using the following code:

String nonEncodedString = mock(String.class);
when(nonEncodedString.getBytes(anyString())).thenThrow(new UnsupportedEncodingException("Parsing error."));

問題是，當(dāng)我運(yùn)行我的測試用例時，我得到一個 MockitoException，它說我無法模擬 java.lang.String 類.

The problem is that when I run my test case I get a MockitoException that says that I can't mock a java.lang.String class.

有沒有辦法使用 mockito 來模擬 String 對象，或者，當(dāng)我調(diào)用 getBytes 方法時，是否可以讓我的 String 對象拋出 UnsupportedEncodingException?

Is there a way to mock a String object using mockito or, alternatively, a way to make my String object throw an UnsupportedEncodingException when I call the getBytes method?

這里有更多細(xì)節(jié)來說明問題:

Here are more details to illustrate the problem:

這是我要測試的類:

public final class A {
    public static String f(String str){
        try {
            return new String(str.getBytes("UTF-8"));
        } catch (UnsupportedEncodingException e) {
            // This is the catch block that I want to exercise.
            ...
        }
    }
}

這是我的測試類(我正在使用 JUnit 4 和 mockito):

This is my testing class (I'm using JUnit 4 and mockito):

public class TestA {

    @Test(expected=UnsupportedEncodingException.class)
    public void test(){
        String aString = mock(String.class);
        when(nonEncodedString.getBytes(anyString())).thenThrow(new UnsupportedEncodingException("Parsing error."));
        A.f(aString);
    }
}

推薦答案

問題是Java中的String類被標(biāo)記為final，所以使用傳統(tǒng)的mocking框架不能mock.根據(jù) Mockito FAQ，這也是該框架的限制.

The problem is the String class in Java is marked as final, so you cannot mock is using traditional mocking frameworks. According to the Mockito FAQ, this is a limitation of that framework as well.

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