Flesh out HSpec with basic example (#402)

Author: ggorlen

content/languages/haskell/hspec.md

@@ -1,4 +1,38 @@
 ---
-title: Hspec
 kind: reference
+sidebar: "language:haskell"
+prev: /languages/haskell/
+languages: [haskell]
+tags:
+  - testing
 ---
+
+# HSpec
+
+## Basic Setup
+
+### Solution Code
+
+```haskell
+module Example where
+
+add :: Num a => a -> a -> a
+add = (+)
+```
+
+### Test Fixture
+
+```haskell
+module ExampleSpec where -- test module name MUST end with Spec
+import Test.Hspec
+import Example
+
+spec :: Spec -- `spec` is required
+spec = do
+  describe "Example" $ do
+    it "add a b" $ do
+      (add 1 1) `shouldBe` (2 :: Integer)
+
+main :: IO () -- `main` is optional
+main = hspec spec
+```