java - 在测试用例中创建构造函数，使其仅被调用一次

Question

尝试创建一个在我的单元测试中只调用一次的构造函数

public class ArtistTest extends InstrumentationTestCase{
    private static final String TAG_NAME = "TESTING_SUITE";
    private TestingMusicDAO musicDAO;
    private List<Song> songs;
    private Instrumentation instr;
    MusicService musicService;

    public ArtistTest() throws Exception {
        super();       
        instr = this.getInstrumentation();
        Log.d(TAG_NAME, "Setting up testing songs");
        musicDAO = new TestingMusicDAO(instr.getContext());
        musicService = new MusicServiceImpl(musicDAO);
        musicDAO.getAllSongsFromFile();
        songs = musicDAO.getAllSongs();
        for(Song song : songs)
            Log.d( TAG_NAME, song.toString() );
    }

但是当我将文件作为 Android Junit 测试运行时，我在构造函数错误中遇到异常。这里还有堆栈跟踪

 junit.framework.AssertionFailedError: Exception in constructor: test0      (java.lang.NullPointerException
 at com.intellimec.ilane.ice.mediaservices.ArtistTest.<init>(ArtistTest.java:17)
 at java.lang.reflect.Constructor.constructNative(Native Method)
 at java.lang.reflect.Constructor.newInstance(Constructor.java:417)
 at junit.runner.BaseTestRunner.getTest(BaseTestRunner.java:118)
 at android.test.AndroidTestRunner.getTest(AndroidTestRunner.java:148)
 at android.test.AndroidTestRunner.setTestClassName(AndroidTestRunner.java:56)
 at   android.test.suitebuilder.TestSuiteBuilder.addTestClassByName(TestSuiteBuilder.java:80)
 at android.test.InstrumentationTestRunner.parseTestClass(InstrumentationTestRunner.java:444)
 at android.test.InstrumentationTestRunner.parseTestClasses(InstrumentationTestRunner.java:425)
 at android.test.InstrumentationTestRunner.onCreate(InstrumentationTestRunner.java:370) 
 at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4382)
 at android.app.ActivityThread.access$1300(ActivityThread.java:141)
 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1294)
 at android.os.Handler.dispatchMessage(Handler.java:99)
 at android.os.Looper.loop(Looper.java:137)
 at android.app.ActivityThread.main(ActivityThread.java:5039)
 at java.lang.reflect.Method.invokeNative(Native Method)
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
 at dalvik.system.NativeStart.main(Native Method)
 )
 at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:190)
 at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:175)
 at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:555)
 at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1661)

Answer 1

将您只需要在测试运行期间执行一次的代码放入静态初始化程序中。它应该只在加载类时运行一次(不要重复使用此类)。