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GHC 9.10.3 · lts/ghc-9.10.x · c74966e · 2026-09-27

Moduleservant-openapi3-2.0.1.6Haskell2010

Servant.OpenApi.Test

Automatic tests for servant API against OpenApi spec.

  • 2 values
valuevalidateEveryToJSON
  1. :: TMap (Every '[Typeable, Show, Arbitrary, ToJSON, ToSchema]) (BodyTypes JSON api)
  2. => proxy api

    Servant API.

  3. -> Spec
#

Verify that every type used with JSON content type in a servant API has compatible ToJSON and ToSchema instances using validateToJSON.

NOTE: validateEveryToJSON does not perform string pattern validation. See validateEveryToJSONWithPatternChecker.

validateEveryToJSON will produce one prop specification for every type in the API. Each type only gets one test, even if it occurs multiple times in the API.

Example7 expressions
data User = User { name :: String, age :: Maybe Int } deriving (Show, Generic, Typeable)newtype UserId = UserId String deriving (Show, Generic, Typeable, ToJSON, Arbitrary)instance ToJSON Userinstance ToSchema Userinstance ToSchema UserIdinstance Arbitrary User where arbitrary = User <$> arbitrary <*> arbitrarytype UserAPI = (Capture "user_id" UserId :> Get '[JSON] User) :<|> (ReqBody '[JSON] User :> Post '[JSON] UserId)
Example1 expression
hspec $ context "ToJSON matches ToSchema" $ validateEveryToJSON (Proxy :: Proxy UserAPI)ToJSON matches ToSchema  User......  UserId......Finished in ... seconds...2 examples, 0 failures...

For the test to compile all body types should have the following instances:

If any of the instances is missing, you'll get a descriptive type error:

Example5 expressions
data Contact = Contact { fullname :: String, phone :: Integer } deriving (Show, Generic)instance ToJSON Contactinstance ToSchema Contacttype ContactAPI = Get '[JSON] Contacthspec $ validateEveryToJSON (Proxy :: Proxy ContactAPI)......No instance for (Arbitrary Contact)...  arising from a use of ‘validateEveryToJSON’...