# hspec-hedgehog
An integration library for [hspec](https://hackage.haskell.org/package/hspec) and [hedgehog](https://hackage.haskell.org/package/hedgehog).
Example:
```haskell
import Control.Concurrent (threadDelay)
import Control.Monad.IO.Class (liftIO)
import qualified Hedgehog.Gen as Gen
import qualified Hedgehog.Range as Range
import Test.Hspec (before, describe, hspec, it, shouldBe)
import Test.Hspec.Hedgehog (PropertyT, diff, forAll, hedgehog,
(/==), (===))
main :: IO ()
main = hspec $ do
describe "regular tests" $ do
it "works" $ do
True `shouldBe` True
describe "hedgehog" $ do
it "is useful if you get an ambiguous error" $ hedgehog $ do
"no ambiguity" === "no ambiguity"
describe "hedgehog tests" $ do
it "lets you use PropertyT directly" $ hedgehog $ do
x <- forAll $ Gen.integral (Range.linear 0 1000)
y <- forAll $ Gen.integral (Range.linear 0 5000)
diff (x + y) (>=) x
it "renders a progress bit" $ hedgehog $ do
x <- forAll $ Gen.integral (Range.linear 0 1000)
y <- forAll $ Gen.integral (Range.linear 1 5000)
liftIO $ threadDelay (100 * x + y)
describe "with hooks" $ do
before (pure "Hello!") $ do
it "has functions" $ \str -> hedgehog $
str === "Hello!"
it "goes before or after" $ \str -> do
pure () :: PropertyT IO ()
str === "Hello!"
it "generates" $ \str -> hedgehog $ do
wrongLen <- forAll $ Gen.integral (Range.linear 0 3)
length str /== wrongLen
```
## How does this differ from [`hw-hspec-hedgehog`](https://hackage.haskell.org/package/hw-hspec-hedgehog)?
Good question!
The `hw-spec-hedgehog` implementation does the easy thing.
It calls Hedgehog's `check` function on the property, and if the property returns `True`, then it passes the test.
If the property fails, then it renders an [uninformative failure message](https://twitter.com/mattoflambda/status/1234879820225400832) - it's hardcoded to be:
> Hedgehog property test failed
And that's all you get!
This library preserves Hedgehog's error message formatting, so you get [rich, insightful error messages](https://twitter.com/mattoflambda/status/1234880271406661633) just like Hedgehog intended.
Furthermore, this library integrates with `hspec`'s support for the `QuickCheck` library.
Any option that works with `QuickCheck` should work with `hedgehog` properties, so you can use `modifyMaxSuccess (\_ -> 10)` to set the total tests to be 10, rather than the default 100.
Because it integrates directly with hspec, it also renders a familiar progress message while the test is running.