Add bench-fibo example as proper benchmark

Also move sources to src/ so there are no accidental rebuilding.

.github/workflows/other.yml

@@ -65,4 +65,4 @@ jobs:
           apt-get install -y ghc libghc-tasty-dev
         run: |
           ghc --version
-          ghc Test/Tasty/Bench.hs
+          ghc src/Test/Tasty/Bench.hs

bench/bench-fibo.hs

@@ -0,0 +1,15 @@
+module Main (main) where
+
+import Test.Tasty.Bench
+
+fibo :: Int -> Integer
+fibo n = if n < 2 then toInteger n else fibo (n - 1) + fibo (n - 2)
+
+main :: IO ()
+main = defaultMain
+  [ bgroup "fibonacci numbers"
+    [ bench "fifth"     $ nf fibo  5
+    , bench "tenth"     $ nf fibo 10
+    , bench "twentieth" $ nf fibo 20
+    ]
+  ]

tasty-bench.cabal

@@ -45,7 +45,7 @@ flag debug
 
 library
   exposed-modules:  Test.Tasty.Bench
-  hs-source-dirs:   .
+  hs-source-dirs:   src
   default-language: Haskell2010
   ghc-options:      -O2 -Wall -fno-warn-unused-imports
   if impl(ghc < 7.10)
@@ -66,3 +66,11 @@ library
 
   if flag(debug)
     cpp-options: -DDEBUG
+
+benchmark bench-fibo
+  default-language: Haskell2010
+  hs-source-dirs:   bench
+  main-is:          bench-fibo.hs
+  type:             exitcode-stdio-1.0
+  build-depends:    base, tasty-bench
+  ghc-options:      "-with-rtsopts=-A32m"