ClassNotFoundException during Android test instrument

I've seen many topics dealing with this error but could not found a working solution. So I'll try to describe the problem completely.

I've got a project and a project test. My project manifest :

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.toto.app"
  android:versionCode="3"
  android:versionName="0.3.1">
  ...
    <application android:icon="@drawable/icon" android:label="@string/app_name">
    ...
    </application>
</manifest>

And my test project manifest :

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.toto.app.test"
  android:versionCode="1"
  android:versionName="1.0">
  <uses-sdk android:minSdkVersion="4" />

  <instrumentation android:targetPackage="com.toto.app" android:name="android.test.InstrumentationTestRunner" />

  <application android:icon="@drawable/icon" android:label="@string/app_name">
    <uses-library android:name="android.test.runner" />
  </application>
</manifest>

Here is the activity i want to test : src/com/toto/app/activity/ListActivity, I've got a LaunchActivity (declared as start activity in manifest) that launch this activity.

And in the test, my ListActivityTest is in the same path (src/com/toto/app/activity). I've also tried with src/com/toto/app/test. The source is :

public class ListActivityTest extends  ActivityInstrumentationTestCase2<LaunchActivity>{

  private Solo solo;

  public ListActivityTest() {
    super(LaunchActivity.class);
  }

  public void setUp() throws Exception {
    solo = new Solo(getInstrumentation(), getActivity());
    solo.wait(2000);
  } 
}

The LaunchActivity seems to be found but when it launch the ListActivity, i've got the error :

% adb shell am instrument -w com.toto.app.test/android.test.InstrumentationTestRunner

com.toto.app.activity.ListActivityTest:INSTRUMENTATION_RESULT: shortMsg=java.lang.ClassNotFoundException INSTRUMENTATION_RESULT: longMsg=java.lang.ClassNotFoundException: com.toto.app.activity.ListActivity in loader dalvik.system.PathClassLoader[/system/framework/android.test.runner.jar:/data/app/com.toto.app.test-2.apk:/data/app/com.toto.app-2.apk]

I don't understand why one class is found and the other is not... It fails in the same way in Eclipse. I tried to use directly ListActivity in the testcase but same error. How does it build this apk to avoid some class ?

This is the full stack when using adb.

The full stack in eclipse logcat :

java.lang.NoClassDefFoundError: com.toto.app.activity.ListActivity
 at com.toto.app.activity.LaunchActivity.onCreate(LaunchActivity.java:19)
 at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1794)
 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1851)
 at android.app.ActivityThread.access$1500(ActivityThread.java:132)
 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1038)
 at android.os.Handler.dispatchMessage(Handler.java:99)
 at android.os.Looper.loop(Looper.java:143)
 at android.app.ActivityThread.main(ActivityThread.java:4293)
 at java.lang.reflect.Method.invokeNative(Native Method)
 at java.lang.reflect.Method.invoke(Method.java:507)
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
 at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: com.toto.app.activity.ListActivity in loader dalvik.system.PathClassLoader[/system/framework/android.test.runner.jar:/data/app/com.toto.app.test-2.apk:/data/app/com.toto.app-1.apk]
 at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:551)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
 ... 14 more