implemented getRung

test/AbacusSpec.hs

@@ -32,6 +32,7 @@ spec = describe "Abacus" $ do
   newAbacusSpec
   getNumBeadsSpec
   getNumRungsSpec
+  getRungSpec
 
 newAbacusSpec :: Spec
 newAbacusSpec = describe "newAbacusSpec" $ mapM_
@@ -73,4 +74,18 @@ getNumRungsSpec = describe "getNumRungs" $ mapM_
     tenRungs = build 10
     build n = fromJust $ newAbacus 10 n
 
+getRungSpec :: Spec
+getRungSpec = describe "getRung" $ mapM_
+  ( \(desc, rung, expected) -> context desc $ let
+    actual = getRung rung abacus
+    in it ("should be " ++ show expected) $
+      actual `shouldBe` expected
+  )
+  [ ( "0th rung",      0,  Just 2  )
+  , ( "last rung",     2,  Just 5  )
+  , ( "negative rung", -1, Nothing )
+  , ( "too large",     3,  Nothing )
+  ] where
+    abacus = Abacus 10 [2, 3, 5]
+
 --jl