Question

Trying to create a constructor that is only called once in my unit tests

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() );
    }

But I get an Exception in constructor error when I run the file as a Android Junit Test. Also here is the stack trace

 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

Put the code you only need to execute one time during test runs into static initializer instead. It should only run once, when the class is loaded (do not reuse this class).