add tests for 'yh' motion

test/normal-yank.sml

@@ -0,0 +1,95 @@
+structure NormalYank =
+struct
+  open Railroad
+  open Railroad.Test
+  open InputMsg
+
+  val yhYank = describe "yank motion 'yh'"
+    [ test "yanks empty string when cursor is at index 0" (fn _ =>
+        let
+          (* arrange *)
+          val originalString = "hello world\n"
+          val app = TestUtils.init originalString
+          val app = AppWith.idx (app, 0)
+
+          (* act *)
+          val app = TestUtils.updateMany (app, "yh")
+
+          (* assert *)
+          val expectedString = ""
+        in
+          TestUtils.expectYank (app, expectedString)
+        end)
+    , test "yanks empty string when character before cursor is a newline"
+        (fn _ =>
+           let
+             (* arrange *)
+             val originalString = "hello\nworld\n"
+             val app = TestUtils.init originalString
+             val app = AppWith.idx (app, 6)
+
+             (* act *)
+             val app = TestUtils.updateMany (app, "yh")
+
+             (* assert *)
+             val expectedString = ""
+           in
+             TestUtils.expectYank (app, expectedString)
+           end)
+    , test "yanks one char to the left when on a non-newline" (fn _ =>
+        let
+          (* arrange *)
+          val originalString = "hello world\n"
+          val app = TestUtils.init originalString
+          val app = AppWith.idx (app, 5)
+
+          (* act *)
+          val app = TestUtils.updateMany (app, "yh")
+
+          (* assert *)
+          val expectedString = "o"
+        in
+          TestUtils.expectYank (app, expectedString)
+        end)
+    , test "yanks 3 chars when count is 3" (fn _ =>
+        let
+          (* arrange *)
+          val originalIdx = 5
+          val originalString = "hello world\n"
+
+          val app = TestUtils.init originalString
+          val app = AppWith.idx (app, originalIdx)
+
+          (* act *)
+          val app = TestUtils.updateMany (app, "3yh")
+
+          (* assert *)
+          val expectedString = "llo"
+        in
+          TestUtils.expectYank (app, expectedString)
+        end)
+    , test
+        "yanks from cursor position to start column when \
+        \count is greater than current column"
+        (fn _ =>
+           let
+             (* arrange *)
+             val originalIdx = 5
+             val originalString = "hello world\n"
+
+             val app = TestUtils.init originalString
+             val app = AppWith.idx (app, originalIdx)
+
+             (* act *)
+             val app = TestUtils.updateMany (app, "9yh")
+
+             (* assert *)
+             val expectedString = "hello"
+           in
+             TestUtils.expectYank (app, expectedString)
+           end)
+    ]
+
+
+  val tests = [yhYank]
+end