Io 使用PowerMockito模拟经过修饰的流

所以我有一个类，它在构造函数中接受OutputStream，并在方法中从中创建一个PrintWriter。问题是如何让这个PrintWriter验证它

Example public Class(OutputStream output) {}
public void foo() {
  PrintWriter writer = new PrintWriter(output);
}

我想做的是：

PrintWriter writer = PowerMockito.mock(PrintWriter.class)
PowerMockito
    .whenNew(PrintWriter.class)
    .withArguments(output)
    .thenReturn(writer);

---

然而，我得到的是，没有与这位作家的互动。任何帮助都将不胜感激。

如果您使用PowerMock配置提供完整的代码片段将更好。然后我可以帮你并给你建议，现在我可能只能猜出什么是错的，但我正在努力：

PrintWriter

有几个构造函数可以接受

OutputStream

，而PowerMock有一个缺陷，当类重载构造函数时只传递参数时，它可能会错误地猜测被模拟的构造函数

还有一个常见的错误，您没有将创建

PrintWriter

实例的类添加到

@PrepareForTest

因此，在我的假设案例的基础上进行了示例：

public class PrintWriterCreator {

    private final PrintWriter printWriter;

    public PrintWriterCreator(OutputStream outputStream) {
        this.printWriter = new PrintWriter(outputStream);
    }

    public void write(String message){
        printWriter.write(message);
    }
}

测试等级：

@RunWith(PowerMockRunner.class)
@PrepareForTest({PrintWriter.class, PrintWriterCreator.class})
public class PrintWriterCreatorTest {


    @Mock
    private OutputStream outputStream;

    @Mock
    private PrintWriter printWriterMock;

    private PrintWriterCreator printWriterCreator;


    @Before
    public void setUp() throws Exception {

        whenNew(PrintWriter.class).withParameterTypes(OutputStream.class).withArguments(eq(outputStream)).thenReturn
                                                                                                       (printWriterMock);

        printWriterCreator = new PrintWriterCreator(outputStream);
    }

    @Test
    public void testWrite() throws Exception {
        String message = "someMessage";
        printWriterCreator.write(message);

        verifyNew(PrintWriter.class).withArguments(outputStream);

        verify(printWriterMock).write(eq(message));
    }


}