implemented moving to top and bottom rungs

test/Abacus/App/ActionsSpec.hs

@@ -33,6 +33,8 @@ spec :: Spec
 spec = describe "Actions" $ do
   moveUpSpec
   moveDownSpec
+  topRungSpec
+  bottomRungSpec
   selRungSpec
   beadLeftSpec
   beadRightSpec
@@ -69,6 +71,18 @@ moveDownSpec = describe "moveDown" $ mapM_
     elsewhere = initialState & rungNum .~ 8
     movedDown = initialState & rungNum .~ 1
 
+topRungSpec :: Spec
+topRungSpec = describe "topRung" $ let
+  state = initialState & rungNum .~ 5
+  in it ("should be " ++ show initialState) $
+    topRung state `shouldBe` initialState
+
+bottomRungSpec :: Spec
+bottomRungSpec = describe "bottomRung" $ let
+  expected = initialState & rungNum .~ 9
+  in it ("should be " ++ show expected) $
+    bottomRung initialState `shouldBe` expected
+
 selRungSpec :: Spec
 selRungSpec = describe "selRung" $ mapM_
   ( \(desc, rung, expected) -> context desc $