add a test for 'dge' motion

temp.txt

@@ -1,3 +1 @@
-hello
+hello!world!again\
-world
-again

test/normal-delete.sml

@@ -2410,6 +2410,31 @@ struct
 
           val actualString = LineGap.toString buffer
 
+          val stringIsExpected = expectedString = actualString
+          val cursorIsExpected = expectedCursor = cursorIdx
+        in
+          Expect.isTrue (stringIsExpected andalso cursorIsExpected)
+        end)
+    , test
+        "deletes only two chars when cursor is \
+        \on an a punctuation char which is immediately preceded \
+        \by an alpha char"
+        (fn _ =>
+           let
+             (* arrange *)
+             val originalString = "hello!world!again\n"
+             val app = TestUtils.init originalString
+             val app = AppWith.idx (app, 5)
+
+             (* act *)
+             val {buffer, cursorIdx, ...} = TestUtils.updateMany (app, "dge")
+
+             (* assert *)
+             val expectedString = "hellworld!again\n"
+             val expectedCursor = 4
+
+             val actualString = LineGap.toString buffer
+
              val stringIsExpected = expectedString = actualString
              val cursorIsExpected = expectedCursor = cursorIdx
            in