add unit tests for generating uniffied diff with empty deltas case

Author: dnaumenko

test/testcase/diffutils/GenerateUnifiedDiffTest.java

@@ -8,6 +8,7 @@
 import java.io.File;
 import java.io.FileReader;
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;
 
@@ -42,6 +43,12 @@ public void testGenerateUnifiedWithOneDelta() throws Exception {
         verify(origLines, revLines);
     }
 
+    public void testGenerateUnifiedDiffWithoutAnyDeltas() throws Exception {
+        List<String> test = Arrays.asList("abc");
+        Patch patch = DiffUtils.diff(test, test);
+        DiffUtils.generateUnifiedDiff("abc", "abc", test, patch, 0);
+    }
+
     public void testDiff_Issue10() throws Exception {
         final List<String> baseLines = fileToLines("test" + FS + "mocks" + FS + "issue10_base.txt");
         final List<String> patchLines = fileToLines("test" + FS + "mocks" + FS + "issue10_patch.txt");