JUnit和Mockito Null指针异常

Question

我有一个名为Pinger Service的类，它调用HttpAdapter打开HttpURLConnection并返回它，然后调用getResponseCode来查明URL是否为200。

我正在尝试模拟HttpURLConnection并使getResponseCode返回404，但是我得到一个空指针异常

测试

package com.uk.jacob.service;

import static org.junit.Assert.*;

import java.io.IOException;
import java.net.HttpURLConnection;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.web.WebAppConfiguration;

import com.uk.jacob.SimplePingApplication;
import com.uk.jacob.adapter.HttpAdapter;
import com.uk.jacob.model.Website;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = SimplePingApplication.class)
@WebAppConfiguration
public class PingerServiceTests {

    @Autowired
    PingerService pingerService;

    @Mock
    HttpAdapter httpAdapter;

    @Mock
    HttpURLConnection mockHttpURLConnection;

    @Test
    public void testPingerServiceReturnsOkWhenServiceIsUp() throws IOException{
        Website website = pingerService.ping("http://devnews.today");

        assertEquals(true, website.ok);
    }

    @Test
    public void testPingerServiceReturnsOkWhenServiceIsNotFound() throws IOException{
        Mockito.when(mockHttpURLConnection.getResponseCode()).thenReturn(404);
        Mockito.when(httpAdapter.createHttpURLConnection("http://devnews.today")).thenReturn(mockHttpURLConnection);

        Website website = pingerService.ping("http://devnews.today");

        assertEquals(false, website.ok);
    }

    @Test
    public void testPingerServiceReturnsOkWhenServiceIsDown(){
        Website website = pingerService.ping("https://jacob.uk.comz");

        assertEquals(false, website.ok);
    }

}

Pinger服务

package com.uk.jacob.service;

import java.net.HttpURLConnection;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.uk.jacob.adapter.HttpAdapter;
import com.uk.jacob.model.Website;

@Component
public class PingerService {

    @Autowired
    HttpAdapter httpAdapter;

    @Autowired
    Website website;

    public Website ping(String urlToPing) {     
        try {
            HttpURLConnection connection = httpAdapter.createHttpURLConnection(urlToPing);

            System.out.println(connection.getResponseCode());

            if(connection.getResponseCode() == 200){
                website.ok = true;
            }
        } catch (Exception e) {
            website.ok = false;
        }

        return website;
    }
}

HttpAdapter

package com.uk.jacob.adapter;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;

import org.springframework.stereotype.Component;

@Component
public class HttpAdapter {
    public HttpURLConnection createHttpURLConnection(String urlToPing) throws IOException{
        URL url = new URL(urlToPing);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();

        connection.setRequestMethod("GET");
        connection.connect();

        return connection;
    }
}

失败追踪

java.lang.NullPointerException
    at com.uk.jacob.service.PingerServiceTests.testPingerServiceReturnsOkWhenServiceIsNotFound(PingerServiceTests.java:44)
    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:483)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:254)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    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)

Answer 1

您使用SpringJUnit4ClassRunner和as far as I know运行测试，@Mock除非您使用MockitoJunitRunner或MockitoAnnotations.initMocks(this);，否则无效。

另请注意，代码中的无会使您的服务使用您的模拟。

这就是你获得NPE的原因，因为你的测试方法中mockHttpURLConnection为空。

Answer 2

用于从HttpAdapter创建HttpUrlConnection创建的url值，即调用httpAdapter.createHttpURLConnection与您传递给pingerService.ping的值不匹配。 devnews.today！= http://devnews.today

检查这两行

Mockito.when（httpAdapter.createHttpURLConnection（ “devnews.today”））thenReturn（mockHttpURLConnection）;

网站website = pingerService.ping（“http://devnews.today”）;

因此，在运行时，HttpUrlConnection实际上是空的mocks默认返回值

Answer 3

Try this and change @Autowired to @InjectMocks in test class.


        @Test
        public void testPingerServiceReturnsOkWhenServiceIsNotFound() throws IOException{  
    Mockito.when(httpAdapter.createHttpURLConnection("http://devnews.today")).thenReturn(mockHttpURLConnection);

    Mockito.when(mockHttpURLConnection.getResponseCode()).thenReturn(404);

            Website website = pingerService.ping("http://devnews.today");

            assertEquals(false, website.ok);
        }

Answer 4

而不是@Autowire PingerService使用@InjectMocks

然后，（因为您正在使用SpringJUnit4ClassRunner.class）添加一个用@Before注释的方法。在该方法中写下MockitoAnnotations.initMocks(this)

如果您不想使用MockitoAnnotations.initMocks(this)，可以使用MockitoJunitRunner

import com.uk.jacob.SimplePingApplication;
import com.uk.jacob.adapter.HttpAdapter;
import com.uk.jacob.model.Website;
import org.mockito.InjectMocks;
import org.mockito.MockitoAnnotations;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = SimplePingApplication.class)
@WebAppConfiguration
public class PingerServiceTests {

    @InjectMocks
    PingerService pingerService;

    @Mock
    HttpAdapter httpAdapter;

    @Mock
    HttpURLConnection mockHttpURLConnection;


    @Before
    public void setUp() {
        MockitoAnnotations.initMocks(this);
    }    

    @Test
    public void testPingerServiceReturnsOkWhenServiceIsUp() throws IOException{
        Website website = pingerService.ping("http://devnews.today");

        assertEquals(true, website.ok);
    }

    @Test
    public void testPingerServiceReturnsOkWhenServiceIsNotFound() throws IOException{
        Mockito.when(mockHttpURLConnection.getResponseCode()).thenReturn(404);
        Mockito.when(httpAdapter.createHttpURLConnection("http://devnews.today")).thenReturn(mockHttpURLConnection);

        Website website = pingerService.ping("http://devnews.today");

        assertEquals(false, website.ok);
    }

    @Test
    public void testPingerServiceReturnsOkWhenServiceIsDown(){
        Website website = pingerService.ping("https://jacob.uk.comz");

        assertEquals(false, website.ok);
    }

}