data = "<img src=\"http://example/foo.jpg\" width=\"100\" height=\"400\">";
        assertNull(transformer.getThumbnailUrl(responseData, getDocument(data)));
    }

    public void test_getThumbnailUrl() throws Exception {
        String data = "<meta property=\"og:image\" content=\"http://example/foo.jpg\" />";
        String expected = "http://example/foo.jpg";
        assertGetThumbnailUrl(data, expected);