junit - 使用 powermockito 模拟 jUnit 测试

Question

我正在尝试模拟以下功能

public class ServerConnection{
        public ServerConnection(ClientConnection cn) {
            super(cn);
        }

    public void setUrl(String url) {      
                this.url = URLUtil.processURL(url);
                try {
                    URL dst = new URL(this.url);
                    InputStream is = dst.openStream();
                    Scanner scanner = new Scanner(is);

                    StringBuilder sb = new StringBuilder();

                    while(scanner.hasNextLine())
                        sb.append(scanner.nextLine()).append("\n");


                    if (validate(sb.toString())) {
                       --------
                    } else {    }
                    is.close();
                    scanner.close();
                } catch (Exception ex) {

                }        
        }

    private boolean validate(String content) {
            JSONParser parser = new JSONParser();
            Boolean isJsonValid = false;
            JSONObject json = null;
            try {
              --------
              //json validation goes here
            } catch (Exception e) {          
            }
            return isJsonValid;
        }

        public void setId(Integer id) {
        if(id == null)
        this.id = 0;
        else
        this.id = id;
        }
}

PowerMockito Junit 代码

@RunWith(PowerMockRunner.class)
@PrepareForTest({PathTest.class })
public class URLTest {
 ServerConnection sc ;
 String URL = "http://test.com";

  @Before
     public void setUp() throws Throwable{              
             ClientConnection con =PathTest.getCon();  // Here getCon() is a static method
             sc = new ServerConnection(con);
             sc.setId(1000); 
     }

@Test
    public void testName() throws Throwable {       

        String expectedResponse = "test";
        URL url = PowerMockito.mock(URL.class);
        HttpURLConnection connection = PowerMockito.mock(HttpURLConnection.class);
        InputStream inputStream = PowerMockito.mock(InputStream.class);
        Scanner scanner = PowerMockito.mock(Scanner.class);

        PowerMockito.whenNew(URL.class).withArguments(URL).thenReturn(url);
        PowerMockito.whenNew(Scanner.class).withArguments(inputStream).thenReturn(scanner);
        PowerMockito.when(scanner.useDelimiter("\\A")).thenReturn(scanner);

        PowerMockito.when(url.openConnection()).thenReturn(connection);

        // Response code mocked here
        PowerMockito.when(connection.getResponseCode()).thenReturn(200);

        PowerMockito.when(connection.getInputStream()).thenReturn(inputStream);
        PowerMockito.when(scanner.hasNext()).thenReturn(true);
        PowerMockito.when(scanner.next()).thenReturn(expectedResponse);

        sc.setUrl(URL);
    }
}

在执行此操作时，我观察到以下错误消息

URLTest
com.objects.URLTest
testName(com.objects.URLTest)
java.lang.ExceptionInInitializerError

    at java.lang.Class.forName0(Native Method)

    at java.lang.Class.forName(Class.java:264)

    at javassist.runtime.Desc.getClassObject(Desc.java:43)

    at javassist.runtime.Desc.getClassType(Desc.java:152)

    at javassist.runtime.Desc.getType(Desc.java:122)

    at javassist.runtime.Desc.getType(Desc.java:78)

    at com.objects.PathTest.getCon(TargetPathTest.java:24)

    at com.objects.URLTest.setUp(URLTest.java:41)

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

    at java.lang.reflect.Method.invoke(Method.java:498)

    at org.junit.internal.runners.MethodRoadie.runBefores(MethodRoadie.java:133)

    at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:96)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:310)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:131)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.access$100(PowerMockJUnit47RunnerDelegateImpl.java:59)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner$TestExecutorStatement.evaluate(PowerMockJUnit47RunnerDelegateImpl.java:147)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.evaluateStatement(PowerMockJUnit47RunnerDelegateImpl.java:107)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:298)

    at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:87)

    at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:50)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:218)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:160)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:134)

    at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)

    at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)

    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:136)

    at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:121)

    at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:57)

    at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:59)

    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)

    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)

    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)

    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)

    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)

    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

Caused by: java.lang.NullPointerException   

    ... 38 more

标签： junitmockitopowermockpowermockito

Answer 1

这段代码有很多问题。

第一个技术答案是：你似乎不知道自己在做什么。您有@PrepareForTest({PathTest.class })这表明您打算模拟该类的静态方法。

但是，您并没有做模拟该类中的静态方法所必需的操作。只需逐步按照他们的文档进行操作即可。我还认为 URL 类是最终的，因此您还必须准备注释该类，以便它与 whenNew() 一起使用！

但是：您应该避免模拟 URL 或 URL 连接对象。只需使用某种依赖注入，并确保您可以将一些模拟实例传递到您的测试代码中，例如使用 Mockito 的 @InjectMocks 注释。从那里，您也可以避免使用静态方法。

长话短说：你的生产代码写得很糟糕，你的单元测试（老实说）很糟糕。你应该认真地退后一步，把那些东西扔掉。然后重新考虑你的生产代码不要直接使用new，不要依赖静态方法。通过这样做，您可以摆脱 PowerMockito，您可以使用普通的 Mockito（嗯，您需要启用最终类的模拟）。但请放心：除非绝对必须，否则使用 PowerMock(ito) 是没有意义的。

然后：不要“发明”模拟代码。阅读教程，并逐步按照它们进行操作。你在模拟你的测试用例中的所有东西，但你应该做完全相反的事情：你只有在绝对没有其他方法来测试你的代码时才模拟东西。而且，当这破坏了您合理地对代码进行单元测试的能力时，您绝对不会将方法设为静态。

（静态有它的位置，但是当它妨碍你时，你做错了！）