rendering of right margin of abacus

src/Abacus/App/Widgets/Internal.hs

@@ -62,6 +62,10 @@ beads a = map
   (rungList a)
 
 abacusRight :: AppState -> [String]
-abacusRight = undefined
+abacusRight a =
+  " " : map
+    (\n -> if n == a^.rungNum then "<" else " ")
+    [0..pred (getNumRungs $ a^.abacus)]
+  ++ [" "]
 
 --jl

test/Abacus/App/Widgets/InternalSpec.hs

@@ -117,7 +117,20 @@ beadsSpec = describe "beads" $ mapM_
       ]
 
 abacusRightSpec :: Spec
-abacusRightSpec = describe "abacusRight" $
-  return ()
+abacusRightSpec = describe "abacusRight" $ mapM_
+  ( \(desc, state, expected) -> context desc $
+    it ("should be " ++ show expected) $
+      abacusRight state `shouldBe` expected
+  )
+  [ ( "initial state", initialState, initRes )
+  , ( "rung 5",        r5State,      r5Res   )
+  , ( "negative rung", negState,     negRes  )
+  ]
+  where
+    r5State  = initialState & rungNum .~ 5
+    negState = initialState & rungNum .~ (-1)
+    initRes  = map (:[]) " <          "
+    r5Res    = map (:[]) "      <     "
+    negRes   = map (:[]) "            "
 
 --jl