diff --git a/test/normal-delete.sml b/test/normal-delete.sml
index 3f1b617..c2d6b98 100644
--- a/test/normal-delete.sml
+++ b/test/normal-delete.sml
@@ -4000,6 +4000,74 @@ struct
            end)
     ]
 
+  val diwDelete = describe "delete motion 'diw' (delete inside word)"
+    [test
+       "deletes middle word when middle word is \
+       \an alphanumeric word surrounded on both sides by spaces"
+       (fn _ =>
+          let
+            (* arrange *)
+            val originalString = "hello abc_123 world\n"
+            val app = TestUtils.init originalString
+
+            val app1 = AppWith.idx (app, 6)
+            val app2 = AppWith.idx (app, 7)
+            val app3 = AppWith.idx (app, 8)
+            val app4 = AppWith.idx (app, 9)
+            val app5 = AppWith.idx (app, 10)
+            val app6 = AppWith.idx (app, 11)
+            val app7 = AppWith.idx (app, 12)
+
+            (* act *)
+            val app1 = TestUtils.updateMany (app1, "diw")
+            val app2 = TestUtils.updateMany (app2, "diw")
+            val app3 = TestUtils.updateMany (app3, "diw")
+            val app4 = TestUtils.updateMany (app4, "diw")
+            val app5 = TestUtils.updateMany (app5, "diw")
+            val app6 = TestUtils.updateMany (app6, "diw")
+            val app7 = TestUtils.updateMany (app7, "diw")
+
+            (* assert *)
+            val expectedString = "hello  world\n"
+            val expectedCursorIdx = 6
+
+            val actualString1 = LineGap.toString (#buffer app1)
+            val actualString2 = LineGap.toString (#buffer app2)
+            val actualString3 = LineGap.toString (#buffer app3)
+            val actualString4 = LineGap.toString (#buffer app4)
+            val actualString5 = LineGap.toString (#buffer app5)
+            val actualString6 = LineGap.toString (#buffer app6)
+            val actualString7 = LineGap.toString (#buffer app7)
+
+            val stringsAreExpected =
+              actualString1 = expectedString
+              andalso actualString2 = expectedString
+              andalso actualString3 = expectedString
+              andalso actualString4 = expectedString
+              andalso actualString5 = expectedString
+              andalso actualString6 = expectedString
+              andalso actualString7 = expectedString
+
+            val actualCursor1 = #cursorIdx app1
+            val actualCursor2 = #cursorIdx app2
+            val actualCursor3 = #cursorIdx app3
+            val actualCursor4 = #cursorIdx app4
+            val actualCursor5 = #cursorIdx app5
+            val actualCursor6 = #cursorIdx app6
+            val actualCursor7 = #cursorIdx app7
+
+            val cursorsAreExpected =
+              actualCursor1 = expectedCursorIdx
+              andalso actualCursor2 = expectedCursorIdx
+              andalso actualCursor3 = expectedCursorIdx
+              andalso actualCursor4 = expectedCursorIdx
+              andalso actualCursor5 = expectedCursorIdx
+              andalso actualCursor6 = expectedCursorIdx
+              andalso actualCursor7 = expectedCursorIdx
+          in
+            Expect.isTrue (stringsAreExpected andalso cursorsAreExpected)
+          end)]
+
   val tests =
     [ dhDelete
     , dlDelete
@@ -4025,5 +4093,6 @@ struct
     , dtDelete
     , dFDelete
     , dTDelete
+    , diwDelete
     ]
 end