问为什么Android test runner报告“空测试套件”？

EN

<?xml version="1.0" encoding="utf-8"?>
<!-- package name must be unique so suffix with "tests" so package loader doesn't ignore us -->
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="nilzor.myapp.tests"
          android:versionCode="1"
          android:versionName="1.0">
    <!-- We add an application tag here just so that we can indicate that
         this package needs to link against the android.test library,
         which is needed when building test cases. -->
    <application>
        <uses-library android:name="android.test.runner"/>
    </application>
    <!--
    This declares that this application uses the instrumentation test runner targeting
    the package of nilzor.myapp.  To run the tests use the command:
    "adb shell am instrument -w nilzor.myapp.tests/android.test.InstrumentationTestRunner"
    -->
    <instrumentation android:name="android.test.InstrumentationTestRunner"
                     android:targetPackage="nilzor.myapp"
                     android:label="Tests for nilzor.myapp"/>
</manifest>

package nilzor.myapp.tests;

public class NilzorSomeTest<T extends Activity> extends ActivityUnitTestCase<T>{
    public NilzorSomeTest(Class<T> activityClass){
        super(activityClass);
    }

    @SmallTest
    public void testBlah(){
        assertEquals(1,1);
    }
}