mighty-metropolis

commit 744b88b537e2fe27aa60224f61518c46183d9fa6
parent 931c4a5941fad976ac6eda09669fcc0c9faf1236
Author: Alex Zarebski <aezarebski@gmail.com>
Date:   Thu, 14 May 2020 13:45:45 +0100

extend testing code by adding some helper functions

Diffstat:
M
test/test/Spec.hs
 | 
50
+++++++++++++++++++++++++++++++++++++++++++++++---

1 file changed, 47 insertions(+), 3 deletions(-)
diff --git a/test/test/Spec.hs b/test/test/Spec.hs
@@ -1,8 +1,52 @@
 import Test.Hspec
 
+withinPercent :: Double -> Double -> Double -> Bool
+withinPercent a 0 _ = a == 0
+withinPercent a b n = d / b < (n / 100)
+  where
+    d = abs (a - b)
+
+mean :: [Double] -> Double
+mean xs = sum xs / n
+  where
+    n = fromIntegral (length xs)
+
+variance :: [Double] -> Double
+variance xs = sum [(x - m) ** 2.0 | x <- xs] / (n - 1)
+  where
+    m = mean xs
+    n = fromIntegral (length xs)
+
+stdDev :: [Double] -> Double
+stdDev = sqrt . variance
+
+stdErr :: [Double] -> Double
+stdErr xs = stdDev xs / sqrt n
+  where
+    n = fromIntegral (length xs)
+
+
+testHelperFunctions :: SpecWith ()
+testHelperFunctions = describe "Testing helper functions" $ do
+  it "test withinPercent works" $ do
+    withinPercent 106 100 5 `shouldBe` False
+    withinPercent 105 100 5 `shouldBe` False
+    withinPercent 104 100 5 `shouldBe` True
+    withinPercent 96 100 5 `shouldBe` True
+    withinPercent 95 100 5 `shouldBe` False
+    withinPercent 94 100 5 `shouldBe` False
+  it "test mean works" $ do
+    withinPercent (mean [1,2,3]) 2 1e-3 `shouldBe` True
+    withinPercent (mean [1..100]) 50.5 1e-3 `shouldBe` True
+    withinPercent (mean [1..1000000]) 500000.5 1e-3 `shouldBe` True
+  it "test variance works" $ do
+    withinPercent (variance [0,1]) 0.5 1e-3 `shouldBe` True
+    withinPercent (variance [1,1,1]) 0 1e-3 `shouldBe` True
+    withinPercent (variance [1..100]) 841.66666666 1e-3 `shouldBe` True
+  it "test stdErr works" $ do
+    withinPercent (stdErr [1..100]) 2.901149 1e-3 `shouldBe` True
+    withinPercent (stdErr [1..1000]) 9.133273 1e-3 `shouldBe` True
 
 main :: IO ()
 main = hspec $ do
-  describe "Prelude.head" $ do
-    it "returns the first element of a list" $ do
-      head [23 ..] `shouldBe` (23 :: Int)
+  testHelperFunctions