由于'java.lang.NullPointerException'，测试无法运行android Instrumentation运行失败

Question

我已查看了此错误的所有其他帖子和教程，但未找到解决方案。

我的应用程序有几个库。我试图在其中一个中运行测试，复制到根应用程序测试文件夹。无论我做什么，它都不会运行。我一直得到相同的空指针。这是令人沮丧的，因为我可以从库中运行它（作为一个独立的，而不是在这个新项目中）

运行配置已设置，我选择，类，选择此测试。我指定了测试运行器android.test.InstrumentationTestRunner

DEVICE SHELL COMMAND: pm install -r "/data/local/tmp/myprojectspath.missionst"
pkg: myprojectspath.missionst
Success


Running tests
Test running startedTest running failed: Instrumentation run failed due to 'java.lang.NullPointerException'
Empty test suite.


    08-23 20:14:09.731  17785-17785/mypath
 E/AndroidRuntime﹕ FATAL EXCEPTION: main
        Process: mypath.mobility, PID: 17785
        java.lang.RuntimeException: Exception thrown in onCreate() of ComponentInfo{mypath.test/android.test.InstrumentationTestRunner}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.ClassLoader android.content.Context.getClassLoader()' on a null object reference
                at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5137)
                at android.app.ActivityThread.access$1600(ActivityThread.java:179)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:145)
                at android.app.ActivityThread.main(ActivityThread.java:5972)
                at java.lang.reflect.Method.invoke(Native Method)
                at java.lang.reflect.Method.invoke(Method.java:372)
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
         Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.ClassLoader android.content.Context.getClassLoader()' on a null object reference
                at android.test.AndroidTestRunner.loadTestClass(AndroidTestRunner.java:87)
                at android.test.AndroidTestRunner.setTestClassName(AndroidTestRunner.java:50)
                at android.test.InstrumentationTestRunner.onCreate(InstrumentationTestRunner.java:379)
                at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5134)
                at android.app.ActivityThread.access$1600(ActivityThread.java:179)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:145)
                at android.app.ActivityThread.main(ActivityThread.java:5972)
                at java.lang.reflect.Method.invoke(Native Method)
                at ja

va.lang.reflect.Method.invoke（Method.java:372）

我的构建文件

apply plugin: 'com.android.application'

android {
    signingConfigs {
        myConfig {
            keyAlias '...'
            storeFile file('...')
            keyPassword 'android'
            storePassword 'android'
        }
    }
    compileSdkVersion 21
    buildToolsVersion '21.1.2'
    defaultConfig {
        applicationId "projectpath"
        minSdkVersion 19
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
        signingConfig signingConfigs.myConfig
        testApplicationId "projectpath.missionst"
        testInstrumentationRunner "android.test.InstrumentationTestRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
            signingConfig signingConfigs.myConfig
        }
        debug {
            signingConfig signingConfigs.myConfig
        }
    }
    lintOptions {
        abortOnError false
    }
    productFlavors {
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile project(':lib_a')
    compile project(':lib_b')
    compile 'com.google.android.gms:play-services:7.5.0'
    compile 'com.squareup.retrofit:retrofit:1.9.0'
    compile 'com.squareup.okhttp:okhttp-urlconnection:2.0.0'
    compile 'com.squareup.okhttp:okhttp:2.0.0'
    compile 'com.github.alamkanak:android-week-view:1.2.3'
    compile 'com.google.maps.android:android-maps-utils:0.3.4'
    compile files('libs/rfc2445-4Mar2011.jar')
    compile 'joda-time:joda-time:2.3'
    compile files('libs/volley.jar')
    compile 'com.google.code.gson:gson:2.3.1'
    compile 'com.android.support:support-v13:22.2.1'
    compile 'com.android.support:gridlayout-v7:22.2.1'
    compile 'com.android.support:appcompat-v7:22.2.1'
}

测试文件     包路径;

import java.io.File;

import android.test.AndroidTestCase;
import lib_a_path.DataUtils;

public class UserNameTest extends AndroidTestCase {

    private DataUtils du;

    public UserNameTest() {
        super();
    }

    protected void setUp() throws Exception {
        super.setUp();
        du = new DataUtils(getContext());
        // It looks like the app is just reinstalled on the development environment
        // and the files are not actually deleted.
        // So we will manually delete the file in the setup phase
        File[] initFile = getContext().getFilesDir().listFiles();
        for (int i = 0; i < initFile.length; i++) {
            initFile[i].delete();
        }
    }

    protected void tearDown() throws Exception {
        super.tearDown();
    }

    public void testSaveAndReadUserName() throws Exception {
        File[] beforeFiles = getContext().getFilesDir().listFiles();
        if (beforeFiles.length > 0) {
            System.out.println("beforeFiles[0] = "+beforeFiles[0].getName());
        }
        assertEquals(beforeFiles.length, 0);
        du.saveUserName("testuser");
        File[] afterFiles = getContext().getFilesDir().listFiles();
        assertEquals(afterFiles.length, 1);
        assertEquals(afterFiles[0].getName(), "userName");
        String realUser = du.getUserName();
        assertEquals(realUser, "testuser");
    }

}