在单元测试的方法中模拟文件，filewriter和csvwriter，抛出NullPointerException

我正在尝试模拟文件创建，FileWriter操作和CsvWriter操作 . 我正在使用EasyMock模拟文件创建，PowerMockito模拟FileWriter和CSVWriter操作 . 即使在模拟文件创建之后，junit也显示出NullPointerException ..

我的代码是，

package example.mypackage.rms.utility;

import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import au.com.bytecode.opencsv.CSVWriter;

public class CSVBeanUtil {
    public static boolean writeToCsv(List<String[]> beanList, Path absPath) throws IOException {
        CSVWriter writer = new CSVWriter(new FileWriter(absPath.toAbsolutePath().toString()),
                CSVWriter.DEFAULT_SEPARATOR, CSVWriter.NO_QUOTE_CHARACTER);
        writer.writeAll(beanList);
        writer.close();
        return false;
    }

}

我的测试班是，

package example.mypackage.rms.unittest;

import static org.junit.Assert.assertEquals;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.util.ArrayList;
import java.util.List;
import example.mypackage.rms.config.AppConfig;
import example.mypackage.rms.entity.GiveUpFile;
import example.mypackage.rms.utility.CSVBeanUtil;
import org.easymock.EasyMock;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
import org.powermock.modules.junit4.PowerMockRunnerDelegate;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.web.WebAppConfiguration;
import au.com.bytecode.opencsv.CSVWriter;

@WebAppConfiguration
@ContextConfiguration(classes = { AppConfig.class })
@PrepareForTest(CSVBeanUtil.class)
@RunWith(PowerMockRunner.class)
@PowerMockRunnerDelegate(SpringJUnit4ClassRunner.class)
public class UTCSVBeanUtil {
    @Test
    public void writeBeanToCsv() throws Exception {
        List<String[]> beanList = new ArrayList<String[]>();
        String[] st = new String[5];
        st[0] = "hai";
        beanList.add(st);
        final File fileMock = EasyMock.createMock(File.class);
        EasyMock.expect(fileMock.toPath()).andReturn(Paths.get("test.csv"));
        PowerMockito.mock(CSVWriter.class);
        PowerMockito.mock(FileWriter.class);
        PowerMockito.whenNew(FileWriter.class).withArguments(new File("test.csv")).thenReturn(null);
        PowerMockito.whenNew(CSVWriter.class)
                .withArguments(null, CSVWriter.DEFAULT_SEPARATOR, CSVWriter.NO_QUOTE_CHARACTER).thenReturn(null);

        /*
         * File createdFile= folder.newFile("myfile.csv");
         * ParseCsvToBean.writeBeanToCsv(beanList, "myfile.csv"); String s =
         * FileUtils.readFileToString(createdFile); //not working
         * assertEquals("hai", s);
         */

        /*
         * File createdFile= folder.newFile("myfile.csv");
         * FileUtils.writeStringToFile(createdFile, "hai"); String s =
         * FileUtils.readFileToString(createdFile); //working
         * assertEquals("hai", s);
         */
        boolean expected = false;
        boolean actual = CSVBeanUtil.writeToCsv(beanList, fileMock.toPath());
        assertEquals(expected, actual);

    }
}

例外的是，

example.mypackage.rms.utility.CSVBeanUtil.writeToCsv（CSVBeanUtil.java:51）中的java.lang.NullPointerException，位于sun.reflect.NativeMethodAccessorImpl的example.mypackage.rms.unittest.UTCSVBeanUtil.writeBeanToCsv（UTCSVBeanUtil.java:114） . 位于org.junit.runners的java.lang.reflect.Method.invoke（未知来源）sun.reflect.DelegatingMethodAccessorImpl.invoke（未知来源）的sun.reflect.NativeMethodAccessorImpl.invoke（未知来源）的.invoke0（本地方法） .model.FrameworkMethod $ 1.runReflectiveCall（FrameworkMethod.java:47）在org.junit.internal.runners.model.ReflectiveCallable.run（ReflectiveCallable.java:12）在org.junit.runners.model.FrameworkMethod.invokeExplosively（FrameworkMethod . java：44）atg.junit.internal.runners.statements.InvokeMethod.evaluate（InvokeMethod.java:17）atg.junit.internal.runners.statements.RunBefores.evaluate（RunBefores.java:26）org.springframework .test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate（RunBeforeTestMethodCallbacks.java:73）at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate（RunAfterTestMethodCallbacks.java:82）在org.junit.rules.ExternalResource $ 1.evaluate（ExternalResource.java:48）在org.junit.rules.RunRules.evaluate （RunRules.java:20）org.springframework.test.context.junit4.statements.SpringRepeat.evaluate（SpringRepeat.java:73）org.junit.runners.ParentRunner.runLeaf（ParentRunner.java:271）at org . springframe.test.context.junit4.SpringJUnit4ClassRunner.runChild（SpringJUnit4ClassRunner.java:224）org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild（SpringJUnit4ClassRunner.java:83）at org.junit.runners.ParentRunner $ 3.run （ParentRunner.java:238）位于org.junit.runners.ParentRunner的org.junit.runners.ParentRunner $ 1.schedule（ParentRunner.java:63）org.junit.runners.ParentRunner.runChildren（ParentRunner.java:236）org.junit.runners.ParentRunner .access $ 000（ParentRunner.java:53）在org.springframework.test.co的org.junit.runners.ParentRunner $ 2.evaluate（ParentRunner.java:229） ntext.junit4.statements.RunBeforeTestClassCallbacks.evaluate（RunBeforeTestClassCallbacks.java:61）org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate（RunAfterTestClassCallbacks.java:68）at org.junit.runners.ParentRunner.run（ ParentRunner.java:309）在org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run（SpringJUnit4ClassRunner.java:163）在org.powermock.modules.junit4.internal.impl.DelegatingPowerMockRunner $ 2.call（DelegatingPowerMockRunner.java:143 ）在org.powermock.modules.junit4.internal.impl.DelegatingPowerMockRunner $在组织2.call（DelegatingPowerMockRunner.java:136）在org.powermock.modules.junit4.internal.impl.DelegatingPowerMockRunner.withContextClassLoader（DelegatingPowerMockRunner.java:127） org.powermock上的org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:106）中的.powermock.modules.junit4.internal.impl.DelegatingPowerMockRunner.run（DelegatingPowerMockRunner.java:136） .modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run（AbstractCommonPowerMockRunner.java:53）在org.powermock.modules.junit4.PowerMockRunner.run（PowerMockRunner.java:59）在org.eclipse.jdt.internal.junit4 .runner.JUnit4TestReference.run（JUnit4TestReference.java:50）atg.eclipse.jdt.internal.junit.runner.TestExecution.run（TestExecution.java:38）org.eclipse.jdt.internal.junit.runner.RemoteTestRunner .runTests（RemoteTestRunner.java:459）处org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests（RemoteTestRunner.java:675）（RemoteTestRunner .java：382）org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main（RemoteTestRunner.java:192）

请帮我解决这个问题......谢谢......