[#26] Property tests: rewind & duplicate

test/Test/Chapter1.hs

@@ -5,14 +5,13 @@ module Test.Chapter1
     ) where
 
 import Test.Hspec (Spec, describe, it, shouldBe)
-
-import qualified Hedgehog.Range as Range (linear)
-import qualified Hedgehog.Gen as Gen (int)
-
 import Test.Hspec.Hedgehog (hedgehog, (===), forAll)
 
 import Chapter1
 
+import qualified Hedgehog.Range as Range (linear)
+import qualified Hedgehog.Gen as Gen (int)
+
 
 chapter1 :: Spec
 chapter1 = describe "Chapter1" $ do
@@ -54,6 +53,8 @@ chapter1normal = describe "Chapter1Normal" $ do
         it "negatives mix " $ mid (-20) (-30) (-10) `shouldBe` (-20)
         it "all equal" $ mid 1 1 1 `shouldBe` 1
         it "all equal, except 1" $ mid 1 1 2 `shouldBe` 1
+        it "all equal, except 1" $ mid 2 1 2 `shouldBe` 2
+        it "all equal, except 1" $ mid 1 2 2 `shouldBe` 2
     describe "Task8: isVowel" $ do
         it "true for vowels" $ all isVowel "aeiou" `shouldBe` True
         it "false for non-vowels" $ isVowel 'c' `shouldBe` False
@@ -66,13 +67,9 @@ chapter1normal = describe "Chapter1Normal" $ do
         it "sumLast2 0 > -10" $ sumLast2 (-9) `shouldBe` 9
         it "sumLast2 -10 > -100" $ sumLast2 (-56) `shouldBe` 11
         it "sumLast2 -100 > -1000" $ sumLast2 (-987) `shouldBe` 15
-    describe "Task 4 & 5 : first and last digit" $ do
-        it "last digit is the first digit of the reversed number" $ hedgehog $ do
-            x <- forAll $ Gen.int (Range.linear (-200) 200)
-            (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)
 
 chapter1advanced :: Spec
-chapter1advanced = describe "Chapter1Advanced" $
+chapter1advanced = describe "Chapter1Advanced" $ do
     describe "Task 10*" $ do
         it "first digit 0" $ firstDigit 0 `shouldBe` 0
         it "first digit 0 < 10" $ firstDigit 9 `shouldBe` 9
@@ -82,3 +79,9 @@ chapter1advanced = describe "Chapter1Advanced" $
         it "first digit 0 > -10" $ firstDigit (-9) `shouldBe` 9
         it "first digit -10 > -100" $ firstDigit (-58) `shouldBe` 5
         it "first digit -100 > -1000" $ firstDigit (-158) `shouldBe` 1
+    describe "Task 4 & 5 : first and last digit" $ do
+        it "last digit is the first digit of the reversed number" $ hedgehog $ do
+            xGen <- forAll $ Gen.int (Range.linear (-200) 200)
+            digit <- forAll $ Gen.int (Range.linear 1 9)
+            let x = if xGen `rem` 10 == 0 then xGen + digit else xGen
+            (firstDigit x :: Int) === (lastDigit (reverseInt x) :: Int)

test/Test/Chapter2.hs

@@ -5,9 +5,13 @@ module Test.Chapter2
     ) where
 
 import Test.Hspec (Spec, describe, it, shouldBe)
+import Test.Hspec.Hedgehog (hedgehog, (===), forAll)
 
 import Chapter2
 
+import qualified Hedgehog.Range as Range
+import qualified Hedgehog.Gen as Gen
+
 
 chapter2 :: Spec
 chapter2 = describe "Chapter2" $ do
@@ -41,6 +45,10 @@ chapter2normal = describe "Chapter2Normal" $ do
         it "one elem" $ duplicate [0] `shouldBe` [0, 0]
         it "two elems" $ duplicate [-1, 0] `shouldBe` [-1, -1, 0, 0]
         it "many elems" $ duplicate [0..5] `shouldBe` [0,0,1,1,2,2,3,3,4,4,5,5]
+    describe "Task6: duplicate property" $ do
+        it "length (duplicate xs) = 2 * length xs" $ hedgehog $ do
+            xs <- forAll $ Gen.list (Range.linear 0 10) Gen.bool
+            length (duplicate xs) === 2 * length xs
     describe "Task7: takeEven" $ do
         it "empty" $ takeEven emptyInts `shouldBe` emptyInts
         it "one elem" $ takeEven [1] `shouldBe` [1]
@@ -69,12 +77,19 @@ chapter2normal = describe "Chapter2Normal" $ do
         it "empty on negative" $ rotate (-5) [1..5] `shouldBe` emptyInts
 
 chapter2advanced :: Spec
-chapter2advanced = describe "Chapter2Advanced" $
+chapter2advanced = describe "Chapter2Advanced" $ do
     describe "Task12*: rewind" $ do
         it "empty" $ rewind emptyInts `shouldBe` emptyInts
         it "one elem" $ rewind [1] `shouldBe` [1]
         it "many elems" $ rewind [1..10] `shouldBe` [10,9..1]
         it "many elems random" $ rewind [5,1,9,56,32,7,11] `shouldBe` [11,7,32,56,9,1,5]
+    describe "Task12*: rewind Properties" $ do
+        it "rewind == reverse" $ hedgehog $ do
+            xs <- forAll $ Gen.list (Range.linear 0 10) Gen.bool
+            rewind xs === reverse xs
+        it "length rewind == length" $ hedgehog $ do
+            xs <- forAll $ Gen.list (Range.linear 0 10) Gen.bool
+            length (rewind xs :: [Bool]) === length xs
 
 emptyInts :: [Int]
 emptyInts = []