测试调用本机方法的代码 [英] Testing code which calls native methods

问题描述

我有这样的课程：

public final class Foo
{
    public native int getBar();

    public String toString()
    {
        return "Bar: " + getBar();
    }
}

请注意 getBar（）使用JNI实现，并且该类是 final 。我想编写一个junit测试来测试 toString（）方法。为此，我需要模拟 getBar（）方法，然后运行原始的 toString（）方法来检查输出。

Please note that getBar() is implemented with JNI and that the class is final. I want to write a junit test to test the toString() method. For this I need to mock the getBar() method and then run the original toString() method to check the output.

我的第一个想法是，这一定是不可能的，但后来我发现 PowerMock 支持根据功能列表测试最终类和本机方法。但到目前为止，我没有成功。我管理的最好的事情就是模拟完整的类，但测试测试了模拟的 toString（）方法，而不是那些没有多大意义的真实方法。

My first thought was that this must be impossible but then I found PowerMock which supports testing final classes and native methods according to the feature list. But so far I had no success with it. The best thing I managed was mocking the complete class but then the test tested the mocked toString() method instead of the real one which doesn't make much sense.

那么如何使用PowerMock从上面测试这个 toString（）方法呢？我更喜欢将PowerMock与 Mockito 一起使用，但如果不可行，我可以使用 EasyMock 。

So how can I use PowerMock to test this toString() method from above? I prefer using PowerMock with Mockito but if this is not possible I have no problem with using EasyMock instead.

推荐答案

找到了。我这样做的方式是正确的。我唯一遗漏的是告诉模拟对象在调用toString时调用原始方法（）。所以它的工作原理如下：

Found it. The way I was doing it was correct. The only thing I missed was telling the mock object to call the original method when toString was called(). So it works like this:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ Foo.class })
public class FooTest
{
    @Test
    public void testToString() throws Exception
    {
        Foo foo = mock(Foo.class);
        when(foo.getBar()).thenReturn(42);
        when(foo.toString()).thenCallRealMethod();
        assertEquals("Bar: 42", foo.toString());
    }
}

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