BonusMalus.spec.hs

  describe "Insurance Bonus system" $ do
    describe "evolution without accident" $ do
      it "starts at 100 for new drivers" $ 
        bonus new `shouldBe` 100
      it "after each year without accident, it decreases by 5%" $ do
        bonus (new >- Year) `shouldBe` 95
        bonus (new >- Year >- Year) `shouldBe` 90
        bonus (years 5) `shouldBe` 76
      it "never goes under 50%" $ do
        bonus (caped) `shouldBe` 50
        bonus (caped >- Year) `shouldBe` 50
    describe "accident effect on bonus" $ do
      it "Liable accidents increase bonus by 25%" $ do
        bonus (new >- (Accident Liable)) `shouldBe` 125
        bonus ((years 6) >- (Accident Liable)) `shouldBe` 90
      it "Split accidents increase bonus by 12.5%" $ do
        bonus (new >- (Accident Split)) `shouldBe` 112
        bonus ((years 6) >- (Accident Split)) `shouldBe` 81
      it "No bonus is acquired the year of an accident" $ do
        bonus (new >- (Accident Liable) >- Year) `shouldBe` 125
        bonus ((years 6) >- (Accident Split) >- Year) `shouldBe` 81
      it "bonus never goes above 350%" $ do
        bonus wrecked `shouldBe` 350
        bonus (wrecked >- (Accident Liable)) `shouldBe` 350
    describe "special rules" $ do
      it "after two years without accidents, coef is reduced to 100 if above" $ do
        bonus (wrecked >- Year >- Year) `shouldBe` 100
        bonus (wrecked >- Year >- Year >- Year) `shouldBe` 95
      it "if coef has been at 50 for 3 years next accident is ignored" $ do
        bonus (caped >- Year >- Year >- Year >- (Accident Liable)) `shouldBe` 50
        
wrecked = foldl (>-) new (replicate 20 (Accident Liable)) 
years n = foldl (>-) new (replicate n Year) 
caped = years 13