STYLE: Increase test style consistency

Increase test style consistency:
- Check the test input arguments at the beginning to conform to the ITK SW
Guide style guidelines. Take advantage of the commit to make the
argument check message consistent with the ITK SW Guide style
guidelines.
- Prefer using `constexpr <type>` to define compile-time constant values.

Modules/Registration/PDEDeformable/test/itkMultiResolutionPDEDeformableRegistrationTest.cxx

@@ -140,24 +140,23 @@ int
 itkMultiResolutionPDEDeformableRegistrationTest(int argc, char * argv[])
 {
 
-  using PixelType = unsigned char;
-  enum
+  if (argc < 2)
   {
-    ImageDimension = 2
-  };
+    std::cerr << "Missing parametes." << std::endl;
+    std::cerr << "Usage: " << itkNameOfTestExecutableMacro(argv) << " WarpedImage" << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  constexpr unsigned int ImageDimension = 2;
+  using PixelType = unsigned char;
+
   using ImageType = itk::Image<PixelType, ImageDimension>;
   using VectorType = itk::Vector<float, ImageDimension>;
   using FieldType = itk::Image<VectorType, ImageDimension>;
   using IndexType = ImageType::IndexType;
   using SizeType = ImageType::SizeType;
   using RegionType = ImageType::RegionType;
 
-  if (argc < 2)
-  {
-    std::cerr << "Usage: " << itkNameOfTestExecutableMacro(argv) << " WarpedImage\n";
-    return EXIT_FAILURE;
-  }
-
   //--------------------------------------------------------
   std::cout << "Generate input images and initial field";
   std::cout << std::endl;