NoClassDefFoundError while trying to run unit tests on Android Studio

Question

I'm trying to create some simple tests for my Android app but I'm running into issues with getting the tests to even run. I keep getting a NoClassDefFound error while I'm trying to run the test, however I can't seem to figure out what the cause of it is. I'd appreciate it if I could get a fresh pair of eyes to look at this.

EDIT: Here is a picture of the structure:

Here's the error that I keep getting:

junit.framework.AssertionFailedError: Exception in constructor: testScanResultNotNull (java.lang.NoClassDefFoundError: nl.hanze.myhealth.ScanResultActivity
at nl.hanze.myhealth.CameraTest.<init>(CameraTest.java:14)
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:149)
at android.test.AndroidTestRunner.setTestClassName(AndroidTestRunner.java:57)
at android.test.suitebuilder.TestSuiteBuilder.addTestClassByName(TestSuiteBuilder.java:80)
at android.test.InstrumentationTestRunner.parseTestClass(InstrumentationTestRunner.java:443)
at android.test.InstrumentationTestRunner.parseTestClasses(InstrumentationTestRunner.java:424)
at android.test.InstrumentationTestRunner.onCreate(InstrumentationTestRunner.java:370)
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4435)
at android.app.ActivityThread.access$1300(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
)
at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:191)
at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:176)
at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:554)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1701)

CameraTest

package nl.hanze.myhealth;

import android.test.ActivityInstrumentationTestCase2;
import android.test.suitebuilder.annotation.SmallTest;

    public class CameraTest extends ActivityInstrumentationTestCase2<ScanResultActivity> {

        ScanResultActivity mActivity;

        public CameraTest(){
            super(ScanResultActivity.class);
        }

        @Override
        protected void setUp()throws Exception{
            super.setUp();
            mActivity = getActivity();
        }

        @SmallTest
        public void testScanResultNotNull(){
            boolean test = mActivity.generateScanResult();
            assertNotNull(test);
        }

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

ScanResultActivity

package nl.hanze.myhealth;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

import java.util.Random;


    public class ScanResultActivity extends Activity {

        Random rand = new Random();

        public ScanResultActivity(){

        }

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_scan_result);
        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.scan_result, menu);
            return true;
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();
            if (id == R.id.action_settings) {
                return true;
            }
            return super.onOptionsItemSelected(item);
        }

        protected boolean generateScanResult(){
            boolean positive_scanresult;
            int max = 10;
            int min = 1;
            int randomNum = rand.nextInt((max - min) + 1) + min;
            if(randomNum >= 6){
                positive_scanresult = true;
            }else{
                positive_scanresult = false;
            }
            return positive_scanresult;
        }
    }

Answer 1

1) Put your tests into package nl.hanze.myhealth.tests. You can do so using Android Studio, or manually:

• create a new folder tests inside ...\app\src\androidTest\java\nl\hanze\myhealth\
• move ApplicationTest.java and CameraTest.java inside ...\app\src\androidTest\java\nl\hanze\myhealth\tests\
• rename the package name in each of your java test files to
  package nl.hanze.myhealth.tests;

2) In you application's build.gradle you need to have:

defaultConfig {
    applicationId "nl.hanze.myhealth"
    testApplicationId "nl.hanze.myhealth.tests"
    ...
}

Rebuild and run. That should be enough.