如何为outputStream编写junit测试。write IO IOException

使用JUnit4+测试异常处理是否如预期的那样的方法可能是这样的(注意,如果没有抛出异常,则需要使测试失败)。

    @Test
    public void testWriteToOutputStreamExceptionHandling() {
        //Dummy object for testing
        OutputStream exceptionThrowingOutputStream = new OutputStream() {
            public void write(byte[] b) throws IOException {
                throw new IOException(); //always throw exception
            }
            public void write(int b) {} //need to overwrite abstract method
        };

        try {
            YourClass.writeToOutputStream(new byte[0], exceptionThrowingOutputStream);
            fail("NetModelStreamingException expected");
        }
        catch (NetModelStreamingException e) {
            //ok
        }
    }

如果在其他测试方法中也需要该虚拟对象,则应在测试用例中声明成员变量,并在 setUp -方法的注释为 @Before . 而且,你可以隐藏 try-catch -通过在 @Test 注解。

这样,代码将如下所示:

private OutputStream exceptionThrowingOutputStream;

@Before
public void setUp() throws Exception {
    exceptionThrowingOutputStream = new OutputStream() {
        @Override
        public void write(byte[] b) throws IOException {
            throw new IOException();
        }
        @Override
        public void write(int b) {}
    };
}

@Test(expected = NetModelStreamingException.class)
public void testWriteToOutputStreamExceptionHandling() throws NetModelStreamingException {
    YourClass.writeToOutputStream(new byte[0], exceptionThrowingOutputStream);
}