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# quickcheck-classes
This library provides sets of properties that should hold for common typeclasses,
along with three (3) simple functions that you can use to test them.
### `lawsCheck`:
A convenience function for testing properties in GHCi.
For example, at GHCi:
```bash
>>> lawsCheck (monoidLaws (Proxy :: Proxy Ordering))
Monoid: Associative +++ OK, passed 100 tests.
Monoid: Left Identity +++ OK, passed 100 tests.
Monoid: Right Identity +++ OK, passed 100 tests.
```
Assuming that the `Arbitrary` instance for `Ordering` is good, we now
have confidence that the `Monoid` instance for `Ordering` satisfies
the monoid laws.
### `lawsCheckMany`:
A convenience function for checking multiple typeclass instances
of multiple types. Consider the following Haskell source file:
```haskell
import Data.Proxy (Proxy(..))
import Data.Map (Map)
import Data.Set (Set)
-- A 'Proxy' for 'Set' 'Int'.
setInt :: Proxy (Set Int)
setInt = Proxy
-- A 'Proxy' for 'Map' 'Int' 'Int'.
mapInt :: Proxy (Map Int Int)
mapInt = Proxy
myLaws :: Proxy a -> [Laws]
myLaws p = [eqLaws p, monoidLaws p]
namedTests :: [(String, [Laws])]
namedTests =
[ ("Set Int", myLaws setInt)
, ("Map Int Int", myLaws mapInt)
]
```
Now, in GHCi:
```bash
>>> lawsCheckMany namedTests
Testing properties for common typeclasses
-------------
-- Set Int --
-------------
Eq: Transitive +++ OK, passed 100 tests.
Eq: Symmetric +++ OK, passed 100 tests.
Eq: Reflexive +++ OK, passed 100 tests.
Monoid: Associative +++ OK, passed 100 tests.
Monoid: Left Identity +++ OK, passed 100 tests.
Monoid: Right Identity +++ OK, passed 100 tests.
Monoid: Concatenation +++ OK, passed 100 tests.
-----------------
-- Map Int Int --
-----------------
Eq: Transitive +++ OK, passed 100 tests.
Eq: Symmetric +++ OK, passed 100 tests.
Eq: Reflexive +++ OK, passed 100 tests.
Monoid: Associative +++ OK, passed 100 tests.
Monoid: Left Identity +++ OK, passed 100 tests.
Monoid: Right Identity +++ OK, passed 100 tests.
Monoid: Concatenation +++ OK, passed 100 tests.
```
### `lawsCheckOne`
A convenience function that allows one to check many typeclass
instances of the same type.
For example, in GHCi:
```bash
>>> lawsCheckOne (Proxy :: Proxy Word) [jsonLaws, showReadLaws]
ToJSON/FromJSON: Encoding Equals Value +++ OK, passed 100 tests.
ToJSON/FromJSON: Partial Isomorphism +++ OK, passed 100 tests.
Show/Read: Partial Isomorphism +++ OK, passed 100 tests.
```
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