Safe Haskell | None |
---|---|
Language | Haskell2010 |
json-assertions
is a library for validating that your JSON encoding matches
what you are actually expecting. It does this by providing you with a DSL to
traverse a JSON document at the same time as you traverse the value that was
encoded. As you traverse the JSON document, you are building up assertions (by
asserting that you expect certain keys and array indices to exist), and you can
also add your own assertions to check the contents of object properties.
JSONTest
is an indexed monad, so you will need to enable RebindableSyntax
and bring indexed monadic bind into scope:
import Prelude hiding (Monad(..)) import Control.Monad.Indexed ((>>>=), ireturn) import Test.JSON.Assertions import Data.Aeson return :: a -> JSONTest i i a return = ireturn (>>=) :: m i j a -> (a -> m j k b) -> m i k b (>>=) = (>>>=)
You can now write tests as an action in the JSONTest
monad. The first index
is the type of the object you wish to encode, and the second parameter is the
type that the test ends in. For example, consider the following:
data Person = Person { personName :: String } instance ToJSON Person where toJSON p = object [ "name" .= personName p ]
We can write a test to check that the JSON encoding of a Person
's name is
correct:
personTest :: JSONTest Person String String personTest = do expectedName <- key "name" assertEq expectedName
For more information, you may wish to read http://ocharles.org.uk/blog/posts/2013-11-24-using-indexed-free-monads-to-quickcheck-json.html.
Tests and Traversals
:: String | JSON Key |
-> (i -> j) | An associated morphism into a substructure of the test environment |
-> JSONTest i j j |
Traverse into the value underneath a specific key in the JSON structure. The return value is the value inside the Haskell value - that is, the result applying the associated morphism.
:: Int | JSON array index |
-> (i -> j) | An associated morphism into a substructure of the test environment |
-> JSONTest i j j |
Traverse the specific index of a JSON array. The return value is the value inside the Haskell value - that is, the result applying the associated morphism.
assertEq :: ToJSON a => a -> JSONTest i i () Source #
Assert that the current JSON value is exactly equal to the result of
calling toJSON
on a value.
stop :: JSONTest a () r Source #
Using stop
discards the indices in the monad, which can help when you
need to isum
multiple tests that end in different states.