added test for http://code.opencv.org/issues/3943;

replaced "const InputArray" with "InputArray" to avoid warnings about "const const _InputArray&"

modules/xfeatures2d/test/test_features2d.cpp

@@ -1240,3 +1240,31 @@ TEST(DISABLED_Features2d_SURF_using_mask, regression)
     FeatureDetectorUsingMaskTest test(SURF::create());
     test.safe_run();
 }
+
+TEST( XFeatures2d_DescriptorExtractor, batch )
+{
+    string path = string(cvtest::TS::ptr()->get_data_path() + "detectors_descriptors_evaluation/images_datasets/graf");
+    vector<Mat> imgs, descriptors;
+    vector<vector<KeyPoint> > keypoints;
+    int i, n = 6;
+    Ptr<SIFT> sift = SIFT::create();
+
+    for( i = 0; i < n; i++ )
+    {
+        string imgname = format("%s/img%d.png", path.c_str(), i+1);
+        Mat img = imread(imgname, 0);
+        imgs.push_back(img);
+    }
+
+    sift->detect(imgs, keypoints);
+    sift->compute(imgs, keypoints, descriptors);
+
+    ASSERT_EQ((int)keypoints.size(), n);
+    ASSERT_EQ((int)descriptors.size(), n);
+
+    for( i = 0; i < n; i++ )
+    {
+        EXPECT_GT((int)keypoints[i].size(), 100);
+        EXPECT_GT(descriptors[i].rows, 100);
+    }
+}