Question

例如，我创建简单的服务

public class MyService {

    public void process() {

        try {
            CustomerMessagesService customerMessagesService = new CustomerMessagesService();
            String message = customerMessagesService.getMessage();

            // another logic which can throw an exception                

            SpamCenterService spamCenterService = new SpamCenterService();
            spamCenterService.sendAdvertise(message);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

此服务每1秒从调度程序呼叫一次。

customerMessagesService返回带有广告文本的消息，或者如果此消息包含非法文本，则引发异常。如果customerMessagesService返回成功文本-发送给spamCenterService，并且如果customerMessagesService抛出异常-则记录该异常。还有另一种逻辑可以在这些服务的调用之间引发异常。此异常也会记录。

现在，我想为此方法创建一个单元测试。但是我不明白如何使用void块来测试try..catch方法。

我创建了这个

public class MyServiceTest {

    private MyService myService;

    @Before
    public void setUp() {
        myService = new MyService();
    }

    @Test
    public void process() {
        myService.process();
    }
}

但这总是成功的，因为处理方法不会引发异常。如何测试此方法？

编辑

我找到了一个解决方案，但我不确定。

公共类MyServiceImpl实现MyService {

    public void process() {
        try {
           doIt();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void doIt() throws Exception {
      CustomerMessagesService customerMessagesService = new CustomerMessagesService();
            String message = customerMessagesService.getMessage();

            // another logic which can throw an exception                

            SpamCenterService spamCenterService = new SpamCenterService();
            spamCenterService.sendAdvertise(message);
    }
}

然后在doIt()中测试MyServiceImpl方法。

Answer 1

简而言之，请执行以下操作：

将对象创建移出方法
创建模拟（例如Mockito）并将其注入
验证模拟是否按预期使用

下面的具体示例：

public class MyService {

    private CustomerMessagesService customerMessagesService;
    private SpamCenterService spamCenterService;

    //inject dependencies
    public MyService(CustomerMessagesService customerMessagesService, SpamCenterService spamCenterService) {
        this.customerMessagesService = customerMessagesService;
        this.spamCenterService = spamCenterService;
    }

    public void process() {
        try {
            String message = customerMessagesService.getMessage();

            // another logic which can throw an exception

            spamCenterService.sendAdvertise(message);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}


public class MyServiceTest {

    private MyService myService;
    // mock dependencies with Mockito
    private CustomerMessagesService customerMessagesService = Mockito.mock(CustomerMessagesService.class);
    private SpamCenterService spamCenterService = Mockito.mock(SpamCenterService.class);

    @Before
    public void setUp() {
        myService = new MyService(customerMessagesService, spamCenterService);
    }

    @Test
    public void process() {
        myService.process();

        Mockito.verify(customerMessagesService).getMessage();
        ArgumentCaptor<String> messageCaptor = ArgumentCaptor.forClass(String.class);
        Mockito.verify(spamCenterService).sendAdvertise(messageCaptor.capture());
        assertThat(messageCaptor.getValue(), is(nullValue()));
    }

    @Test
    public void processWithSpecificCustomerMessageServiceBehaviour() {
        Mockito.given(customerMessagesService.getMessage()).willReturn("expectedString");

        myService.process();

        ArgumentCaptor<String> messageCaptor = ArgumentCaptor.forClass(String.class);
        Mockito.verify(spamCenterService).sendAdvertise(messageCaptor.capture());
        assertThat(messageCaptor.getValue(), is("expectedString"));
    }

    @Test
    public void processCatchExceptions() {
        Mockito.given(customerMessagesService.getMessage()).willThrow(new Exception("Bad message"));

        myService.process();

        // if exception is thrown then the code should not reach spamCenterService.sendAdvertise()
        Mockito.verify(spamCenterService, Mockito.never()).sendAdvertise(Mockito.anyString());
    }
}

请注意，您还可以设置模拟程序以抛出特定的异常或返回特定的值，以便可以测试所有可能的情况。

如何使用try ... catch在内部创建void方法的单元测试？

1 个答案: