Why won't the WebView fire onPageLoaded when occurring within a unit test?

I have the following test code:

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

    final CountDownLatch lock = new CountDownLatch(1);

    Client client = new Client(getInstrumentation().getTargetContext(),  new IJavascriptLoadedListener() {
        @Override
        public void onLoaded() {
             lock.countDown();
        }

    lock.await();
}));

and the client class looks like this:

public Client(Context context, Uri path, IJavascriptLoadedListener listener){
    mContext = context;

    mLoadedListener = listener;

    //Load the the webview context for processing jay javascript
    mWebView = new WebView(context);

    mWebView.setWebViewClient(new WebViewClient(){
        @Override
        public void onPageFinished(WebView view, String url) {
            super.onPageFinished(view, url);

            if (mLoadedListener != null) {
                mLoadedListener.onLoaded();
            }
        }
    });

    mWebView.loadUrl("http://www.google.com");
}

This code runs fine when I am running the application, onPageFinished is called. When I run the same thing from a unit test, onPageFinished never gets called. Any idea what I am doing wrong?