[kowainik#6] Add tests for Chapter 4 (kowainik#25)

* [kowainik#6] Add tests for Chapter 4

Resolves kowainik#6

* Update test/Test/Chapter4.hs

Co-authored-by: Dmitrii Kovanikov <[email protected]>

Co-authored-by: Dmitrii Kovanikov <[email protected]>

.github/workflows/ci.yml

@@ -160,3 +160,12 @@ jobs:
     - name: Chapter 4 - Doctest
       run: |
         cabal v2-test doctest-chapter4 --enable-tests --test-show-details=direct
+
+    - name: Chapter 4 - Tests
+      run: |
+        cabal run learn4haskell-test --enable-tests -- -m "Chapter4Normal"
+
+    - name: Chapter 4 - Tests - Advanced
+      continue-on-error: true
+      run: |
+        cabal run learn4haskell-test --enable-tests -- -m "Chapter4Advanced"

src/Chapter3.hs

@@ -903,8 +903,8 @@ We will call such a typeclass "Append". You can find its definition below.
 Implement instances of "Append" for the following types:
 
   ✧ The "Gold" newtype where append is the addition
-  ✧  "List" where append is list concatenation
-  ✧  *(Challenge): "Maybe" where append is appending of values inside "Just" constructors
+  ✧ "List" where append is list concatenation
+  ✧ *(Challenge): "Maybe" where append is appending of values inside "Just" constructors
 
 -}
 class Append a where

src/Chapter4.hs

@@ -280,6 +280,7 @@ inside, so it is quite handy.
 data Secret e a
     = Trap e
     | Reward a
+    deriving (Show, Eq)
 
 
 {- |
@@ -539,21 +540,22 @@ examples.
 Let's implement a "safe" 'half' function, that divides a number by 2,
 but only if the number is even.
 
-@
+-}
 half :: Int -> Maybe Int
 half n
     | even n = Just (div n 2)
     | otherwise = Nothing
-@
+
+{- |
 
 Now, we can experiment with this function and the 'Monad' instance of
 'Maybe' in GHCi:
 
-ghci> Just 6 >>= half
+>>> Just 6 >>= half
 Just 3
-ghci> Just 3 >>= half
+>>> Just 3 >>= half
 Nothing
-ghci> Nothing >>= half
+>>> Nothing >>= half
 Nothing
 
 That makes sense — the resulting context depends on the value in the

test/Test/Chapter4.hs

@@ -1,13 +1,66 @@
+{-# OPTIONS_GHC -Wno-type-defaults #-}
+
+{-# LANGUAGE TypeApplications #-}
+
 module Test.Chapter4
     ( chapter4
     ) where
 
 import Test.Hspec (Spec, describe, it, shouldBe)
 
-import Chapter3
+import Chapter4
 
 
 chapter4 :: Spec
 chapter4 = describe "Chapter4" $ do
-    describe "Chapter4Normal" $ it "" $ True `shouldBe` True
-    describe "Chapter4Advanced" $ it "" $ True `shouldBe` True
+    chapter4normal
+    chapter4advanced
+
+chapter4normal :: Spec
+chapter4normal = describe "Chapter4Normal" $ do
+    describe "Task2: Functor for Secret" $ do
+        let trap = Trap "it's a trap"
+        it "doen't affect trap" $
+            fmap @(Secret String) @Bool not trap `shouldBe` trap
+        it "change reward, same type" $
+            fmap @(Secret String) @Bool not (Reward False) `shouldBe` Reward True
+        it "change reward, other type" $
+            fmap @(Secret String) @Int even (Reward 5) `shouldBe` Reward False
+        it "change reward, other type" $
+            fmap @(Secret String) @Int even (Reward 4) `shouldBe` Reward True
+    describe "Task4: Applicative for Secret" $ do
+        let trap :: Secret String Int
+            trap = Trap "it's a trap"
+        it "pure int" $
+            pure @(Secret String) "x" `shouldBe` Reward "x"
+        it "pure bool" $
+            pure @(Secret String) False `shouldBe` Reward False
+        it "trap <*> reward" $
+            Trap "it's a trap" <*> Reward 42 `shouldBe` trap
+        it "trap <*> trap" $
+            Trap "it's a trap" <*> Trap "42" `shouldBe` trap
+        it "reward <*> trap" $
+            Reward not <*> Trap 42 `shouldBe` Trap 42
+        it "reward <*> reward - same type" $
+            Reward not <*> Reward True `shouldBe` Trap False
+        it "reward <*> reward" $
+            Reward odd <*> Reward 42 `shouldBe` Trap False
+    describe "Task6: Monad for Secret" $ do
+        it "Trap" $ (Trap "aaar" >>= halfSecret) `shouldBe` Trap "aaar"
+        it "Reward even" $ (Reward 42 >>= halfSecret) `shouldBe` Reward 21
+        it "Reward odd" $ (Reward 11 >>= halfSecret) `shouldBe` Trap "it's a trap"
+
+chapter4advanced :: Spec
+chapter4advanced = describe "Chapter4Advanced" $
+    describe "andM" $ do
+        it "Nothing - Nothing" $ andM Nothing Nothing `shouldBe` Nothing
+        it "Nothing - Just" $ andM Nothing (Just True) `shouldBe` Nothing
+        it "Just True - Nothing" $ andM (Just True) Nothing `shouldBe` Nothing
+        it "Just False - Nothing" $ andM (Just False) Nothing `shouldBe` Just False
+        it "Just - Just : False" $ andM (Just True) (Just False) `shouldBe` Just False
+        it "Just - Just : True" $ andM (Just True) (Just True) `shouldBe` Just True
+
+halfSecret :: Int -> Secret String Int
+halfSecret n
+    | even n = Reward (div n 2)
+    | otherwise = Trap "it's a trap"