Mocking up WifiManager for Android Unit Testing

Question

I\'m trying to implement some unit tests for a couple of classes that rely on WifiManager and the returned ScanResults. What I\'d like to do is be able to control the ScanR

Answer 1

I've been struggling for a while to build ScanResult object. I have successfully used that reflection approach above.

If somebody is searching for a way to clone ScanResult object (or any other object implementing Parcelable interface) you can use this approach (I checked it right in a unit test):

@RunWith(RobolectricTestRunner.class)
@Config(manifest=Config.NONE)
public class MovingAverageQueueTests {
    @Test
    public void parcelTest() {
        Parcel parcel = Parcel.obtain();

        ScanResult sr = buildScanResult("01:02:03:04:05:06", 70);

        parcel.writeValue(sr);
        parcel.setDataPosition(0); // required after unmarshalling
        ScanResult clone = (ScanResult)parcel.readValue(ScanResult.class.getClassLoader());
        parcel.recycle();

        assertThat(clone.BSSID, is(equalTo(sr.BSSID)));
        assertThat(clone.level, is(equalTo(sr.level)));
        assertThat(clone, is(not(sameInstance(sr))));
    }

    private ScanResult buildScanResult(String mac, int level) {
        Constructor ctor = null;
        ScanResult sr = null;

        try {
            ctor = ScanResult.class.getDeclaredConstructor(null);
            ctor.setAccessible(true);
            sr = ctor.newInstance(null);

            sr.BSSID = mac;
            sr.level = level;

        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        return sr;
    }
}

And as for performance, this naive check:

@Test
public void buildVsClonePerformanceTest() {
    ScanResult sr = null;

    long start = System.nanoTime();
    for (int i = 0; i < 1000000; i++) {
        sr = buildScanResult("01:02:03:04:05:06", 70);
    }
    long elapsedNanos = System.nanoTime() - start;

    LOGGER.info("buildScanResult: " + elapsedNanos);

    start = System.nanoTime();
    for (int i = 0; i < 1000000; i++) {
        sr = cloneScanResult(sr);
    }
    elapsedNanos = System.nanoTime() - start;

    LOGGER.info("cloneScanResult: " + elapsedNanos);
}

Showed these results:

Oct 26, 2016 3:25:19 PM com.example.neutrino.maze.MovingAverageQueueTests buildVsClonePerformanceTest INFO: buildScanResult: 202072179 Oct 26, 2016 3:25:21 PM com.example.neutrino.maze.MovingAverageQueueTests buildVsClonePerformanceTest INFO: cloneScanResult: 2004391903

So cloning this way is 10 times less effective than creating instance even with reflection. I know this test is not robust as optimizations are done while compiling... However factor of ten is difficult to mitigate. I did also tested 10K iterations and then the factor was even 100! Just for your information.

P.S. getting Parcel.obtain() and parcel.recycle out of loop doesn't help