Scaffold ring buffer with simple Property

2023-03-17/README.md

@@ -6,6 +6,15 @@
 
 ## Retrospective
 
+* There were more people, 6 of us?
+* We did not go very far and as always wasted time setting up the environment which never work out of the box :(
+* Goal was to implement a fixed size LIFO buffer using TDD
+  * The problem is interesting esp. on the testing side -> what tests to write
+  * we stopped before generalising to more than 1 place buffer
+  * we did not try to write one or more interesting Property
+  * we did tiny steps not assuming any prior knowledge => maybe a Property would have helped and lead us to do bigger steps
+* Teh problem is instersting also because it's in IO which is not where Haskell usually shines -> make good IO/statefule code in Haskell  is still tricky
+
 ## Topic
 
 Proposals:
@@ -14,4 +23,4 @@ Proposals:
 |---------------|----------|------------|------|
 | Ring buffer   | Haskell  | Randori    | xxxx |
 
-**Topic selected: **
+**Topic selected: Ring Buffer**

2023-03-17/ringbuffer/CHANGELOG.md

@@ -0,0 +1,5 @@
+# Revision history for ringbuffer
+
+## 0.1.0.0 -- YYYY-mm-dd
+
+* First version. Released on an unsuspecting world.

2023-03-17/ringbuffer/ringbuffer.cabal

@@ -0,0 +1,50 @@
+cabal-version:      2.4
+name:               ringbuffer
+version:            0.1.0.0
+
+-- A short (one-line) description of the package.
+-- synopsis:
+
+-- A longer description of the package.
+-- description:
+
+-- A URL where users can report bugs.
+-- bug-reports:
+
+-- The license under which the package is released.
+-- license:
+author:             IOG Engineering
+maintainer:         engineering@iohk.io
+
+-- A copyright notice.
+-- copyright:
+-- category:
+extra-source-files: CHANGELOG.md
+
+library
+    exposed-modules:  MyLib
+
+    -- Modules included in this library but not exported.
+    -- other-modules:
+
+    -- LANGUAGE extensions used by modules in this package.
+    -- other-extensions:
+    build-depends:    base ^>=4.16.4.0
+    hs-source-dirs:   src
+    default-language: Haskell2010
+
+test-suite tests
+  ghc-options:        -threaded -rtsopts -with-rtsopts=-N
+  hs-source-dirs:     test
+  other-modules:      RingBufferSpec
+  main-is:            Spec.hs
+  type:               exitcode-stdio-1.0
+  build-depends:
+    , base
+    , hspec
+    , hspec-core
+    , QuickCheck
+    , vector
+    , ringbuffer
+  build-tool-depends: hspec-discover:hspec-discover
+  ghc-options:        -threaded -rtsopts

2023-03-17/ringbuffer/src/MyLib.hs

@@ -0,0 +1,4 @@
+module MyLib (someFunc) where
+
+someFunc :: IO ()
+someFunc = putStrLn "someFunc"

2023-03-17/ringbuffer/test/RingBufferSpec.hs

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+module RingBufferSpec where
+
+import Control.Monad (liftM)
+import Data.IORef (IORef, newIORef, readIORef, writeIORef)
+import Test.Hspec (Spec, it, pending, shouldBe, shouldReturn)
+import Test.Hspec.QuickCheck (prop)
+import Test.QuickCheck (Property, arbitrary, forAll)
+import Test.QuickCheck.Monadic (assert, monadicIO, run)
+
+-- a "ring" buffer where you can:
+-- - push an element to the tail if not full
+-- - pop an element from the head if not empty
+-- - fixed capacity in the queue
+
+spec :: Spec
+spec =
+    prop "pushing an element then popping it gives back same element" pushPopIsIdempotence
+
+pushPopIsIdempotence :: Property
+pushPopIsIdempotence = forAll arbitrary $ \x -> monadicIO $ do
+    y <- run $ do
+        buffer <- newBuffer
+        push buffer x
+        pop buffer
+
+    assert (x == y)
+
+pop :: RingBuffer -> IO Int
+pop (RingBuffer b) = readIORef b
+
+push :: RingBuffer -> Int -> IO ()
+push (RingBuffer b) x = writeIORef b x
+
+data RingBuffer = RingBuffer (IORef Int)
+
+newBuffer :: IO RingBuffer
+newBuffer = liftM RingBuffer (newIORef 0)

2023-03-17/ringbuffer/test/Spec.hs

@@ -0,0 +1 @@
+{-# OPTIONS_GHC -F -pgmF hspec-discover  #-}