add Problem7 and Problem7 Test Code of 99 Questions in Haskell Wiki

Author: 7vk1

src/Wiki_99_Questions/Problem8.hs

@@ -0,0 +1,10 @@
+-- Problem8
+-- Eliminate consecutive duplicates of list elements.
+-- If a list contains repeated elements they should be replaced with a single copy of the element. 
+-- The order of the elements should not be changed. 
+
+module Wiki_99_Questions.Problem8 where
+import Data.List
+
+compress :: Eq a => [a] -> [a]
+compress = map head . group

studying-haskell.cabal

@@ -22,6 +22,7 @@ library
                      , Wiki_99_Questions.Problem5
                      , Wiki_99_Questions.Problem6
                      , Wiki_99_Questions.Problem7
+                     , Wiki_99_Questions.Problem8
                      , Lib
   build-depends:       base >= 4.7 && < 5
   default-language:    Haskell2010

test/Wiki_99_Questions/Problem8Spec.hs

@@ -0,0 +1,14 @@
+module Wiki_99_Questions.Problem8Spec where
+
+import Test.Hspec
+import Wiki_99_Questions.Problem8
+
+spec :: Spec
+spec = do
+  describe "Test1 for Problem8" $ do
+    it "compress \"aaaabbbccc\"  -> \"abc\" " $ do
+      compress "aaaabbbccc" `shouldBe` "abc"
+
+  describe "Test2 for Problem9" $ do
+    it "compress \"Haskellllll\" -> \"Haskel\"" $ do
+      compress "Haskellllll" `shouldBe` "Haskel"