ENH: Add test for itkPointsLocator with distances

Check if the size of the returned distance vector is same
as the returned points and the returned distances are accurate.

Modules/Registration/Common/test/itkPointsLocatorTest.cxx

@@ -18,6 +18,7 @@
 
 #include "itkPointsLocator.h"
 #include "itkMapContainer.h"
+#include "itkTestingMacros.h"
 
 template <typename TPointsContainer>
 int
@@ -66,7 +67,7 @@ testPointsLocatorTest()
   typename PointsLocatorType::PointIdentifier pointId = pointsLocator->FindClosestPoint(coords);
   if (pointId != 49)
   {
-    std::cerr << "Error with FindClosestPoint()" << std::endl;
+    std::cerr << "Error with FindClosestPoint(), poindId does not match" << std::endl;
     return EXIT_FAILURE;
   }
 
@@ -77,36 +78,52 @@ testPointsLocatorTest()
   pointsLocator->FindClosestNPoints(coords, 10u, neighborhood);
   if (neighborhood.size() != 10)
   {
-    std::cerr << "Error with FindClosestNPoints()" << std::endl;
+    std::cerr << "Error with FindClosestNPoints(), size of returned points does not match" << std::endl;
     return EXIT_FAILURE;
   }
 
-  std::cout << "Test:  Search() 1" << std::endl;
-
-  pointsLocator->Search(coords, 10u, neighborhood);
-  if (neighborhood.size() != 10)
+  std::cout << "Test:  FindClosestNPoints() with distances  (1)" << std::endl;
+  std::vector<double> distances;
+  pointsLocator->FindClosestNPoints(coords, 10u, neighborhood, distances);
+  if (neighborhood.size() != 10 || distances.size() != 10)
   {
-    std::cerr << "Error with Search() 1" << std::endl;
+    std::cerr << "Error with FindClosestNPoints(), size of returned points or distances does not match" << std::endl;
     return EXIT_FAILURE;
   }
 
-  double radius = std::sqrt(3 * itk::Math::sqr(5.1));
-
-  std::cout << "Test:  FindPointsWithinRadius()" << std::endl;
+  // Check if returned distances are correct
+  for (unsigned int i = 0; i < neighborhood.size(); ++i)
+  {
+    auto dist = coords.EuclideanDistanceTo(points->GetElement(neighborhood[i]));
+    ITK_TEST_EXPECT_EQUAL(dist, distances[i]);
+    std::cout << dist << " + " << distances[i] << std::endl;
+  }
 
-  pointsLocator->FindPointsWithinRadius(coords, radius, neighborhood);
-  if (neighborhood.size() != 11)
+  std::cout << "Test:  FindClosestNPoints() with distances  (2)" << std::endl;
+  pointsLocator->FindClosestNPoints(coords, 200u, neighborhood, distances);
+  if (neighborhood.size() != 100 || distances.size() != 100)
   {
-    std::cerr << "Error with FindPointsWithinRadius()" << std::endl;
+    std::cerr << "Error with FindClosestNPoints(), size of returned points or distances is incorrect" << std::endl;
     return EXIT_FAILURE;
   }
 
-  std::cout << "Test:  Search() 2" << std::endl;
+  // Check if returned distances are correct
+  for (unsigned int i = 0; i < neighborhood.size(); ++i)
+  {
+    auto dist = coords.EuclideanDistanceTo(points->GetElement(neighborhood[i]));
+    ITK_TEST_EXPECT_EQUAL(dist, distances[i]);
+    std::cout << dist << " * " << distances[i] << std::endl;
+  }
+
+  double radius = std::sqrt(3 * itk::Math::sqr(5.1));
+
+  std::cout << "Test:  FindPointsWithinRadius()" << std::endl;
 
-  pointsLocator->Search(coords, radius, neighborhood);
+  pointsLocator->FindPointsWithinRadius(coords, radius, neighborhood);
   if (neighborhood.size() != 11)
   {
-    std::cerr << "Error with Search() 2" << std::endl;
+    std::cerr << "Error with FindPointsWithinRadius(), size of returned points within radius does not match"
+              << std::endl;
     return EXIT_FAILURE;
   }