Fix MergeWithSameNamedOCGTest test to do not accept possible false positive

DEVSIX-6093

Author: vitali.prudnikovich

kernel/src/main/java/com/itextpdf/kernel/pdf/OcgPropertiesCopier.java

@@ -233,6 +233,8 @@ private static void copyOCGs(Set<PdfIndirectReference> fromOcgsToCopy, PdfDictio
 
             String currentLayerName = toOcg.getAsString(PdfName.Name).toUnicodeString();
 
+            // Here we check on existed layer names only in destination document but not in source document.
+            // That is why there is no something like layerNames.add(currentLayerName); after this if statement
             if (layerNames.contains(currentLayerName)) {
                 hasConflictingNames = true;
                 int i = 0;

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfWriter.java

@@ -285,7 +285,8 @@ protected PdfObject copyObject(PdfObject obj, PdfDocument documentTo, boolean al
         }
 
         SerializedObjectContent serializedContent = null;
-        if (properties.smartMode && tryToFindDuplicate && !checkTypeOfPdfDictionary(obj, PdfName.Page) && !checkTypeOfPdfDictionary(obj, PdfName.OCG)) {
+        if (properties.smartMode && tryToFindDuplicate && !checkTypeOfPdfDictionary(obj, PdfName.Page) &&
+                !checkTypeOfPdfDictionary(obj, PdfName.OCG)) {
             serializedContent = smartModeSerializer.serializeObject(obj);
             PdfIndirectReference objectRef = smartModeSerializer.getSavedSerializedObject(serializedContent);
             if (objectRef != null) {

kernel/src/test/java/com/itextpdf/kernel/utils/PdfMergerTest.java

@@ -538,6 +538,8 @@ public void MergeWithSameNamedOCGTest() throws IOException, InterruptedException
         }
 
         Assert.assertNull(new CompareTool().compareByContent(mergedDocument, cmpDocument, destinationFolder));
+        // We have to compare visually also because compareByContent doesn't catch the differences in OCGs with the same names
+        Assert.assertNull(new CompareTool().compareVisually(mergedDocument, cmpDocument, destinationFolder, "diff_"));
     }
 
     private void mergePdfs(List<File> sources, String destination) throws IOException {