diff --git a/CHANGELOG.md b/CHANGELOG.md
index ecc03af..129621e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@ and this project adheres to
 [Haskell Package Versioning Policy](https://pvp.haskell.org/).
 
 ## [Unreleased]
+## Changed
+- `Test.Hspec.GraphQL.*`: replace `IO` in the resolver with any `MonadCatch`.
 
 ## [0.9.0.0] - 2020-07-24
 ## Fixed
diff --git a/README.md b/README.md
index 917da40..065645a 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,9 @@
-# Haskell GraphQL
+# GraphQL implementation in Haskell.
 
 [![Hackage Version](https://img.shields.io/hackage/v/graphql.svg)](https://hackage.haskell.org/package/graphql)
 [![Build Status](https://github.com/caraus-ecms/graphql/workflows/Haskell%20CI/badge.svg)](https://github.com/caraus-ecms/graphql/actions?query=workflow%3A%22Haskell+CI%22)
 [![License](https://img.shields.io/badge/license-BSD--3--Clause-blue.svg)](https://raw.githubusercontent.com/caraus-ecms/graphql/master/LICENSE)
-
-GraphQL implementation in Haskell.
+[![Simple Haskell](https://www.simplehaskell.org/badges/badge.svg)](https://www.simplehaskell.org)
 
 This implementation is relatively low-level by design, it doesn't provide any
 mappings between the GraphQL types and Haskell's type system and avoids
@@ -13,12 +12,19 @@ be built on top of it.
 
 ## State of the work
 
-For now this only provides a parser and a printer for the GraphQL query language
-and allows to execute queries and mutations using the given schema, but without
-the validation step. But the idea is to be a Haskell port of
+For now this library provides:
+
+- Parser for the query and schema languages, as well as a printer for the query
+  language (minimizer and pretty-printer).
+- Data structures to define a type system.
+- Executor (queries, mutations and subscriptions are supported).
+- Validation is work in progress.
+- Introspection isn't available yet.
+
+But the idea is to be a Haskell port of
 [`graphql-js`](https://github.com/graphql/graphql-js).
 
-For the list of currently missing features see issues marked as
+For a more precise list of currently missing features see issues marked as
 "[not implemented](https://github.com/caraus-ecms/graphql/labels/not%20implemented)".
 
 ## Documentation
diff --git a/graphql.cabal b/graphql.cabal
index 6ac951a..73e71e7 100644
--- a/graphql.cabal
+++ b/graphql.cabal
@@ -4,7 +4,7 @@ cabal-version: 1.12
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 5fa34f11ab1242b72c75c3c19b31ba310c24716a0eb2d134d2b17dd558280732
+-- hash: 1d8c32c00a882ccd1fefc4c083d5fe4e83a1825fbf8e0dcfd551ff2c8cd2dda0
 
 name:           graphql
 version:        0.9.0.0
@@ -24,12 +24,10 @@ license-file:   LICENSE
 build-type:     Simple
 extra-source-files:
     CHANGELOG.md
-    README.md
+    CONTRIBUTING.md
     LICENSE
+    README.md
     docs/tutorial/tutorial.lhs
-data-files:
-    tests/data/kitchen-sink.graphql
-    tests/data/kitchen-sink.min.graphql
 
 source-repository head
   type: git
@@ -91,7 +89,6 @@ test-suite tasty
       Language.GraphQL.ValidateSpec
       Test.DirectiveSpec
       Test.FragmentSpec
-      Test.KitchenSinkSpec
       Test.RootOperationSpec
       Test.StarWars.Data
       Test.StarWars.QuerySpec
diff --git a/package.yaml b/package.yaml
index dcdc6c8..b7098ee 100644
--- a/package.yaml
+++ b/package.yaml
@@ -17,14 +17,11 @@ author:
 
 extra-source-files:
 - CHANGELOG.md
-- README.md
+- CONTRIBUTING.md
 - LICENSE
+- README.md
 - docs/tutorial/tutorial.lhs
 
-data-files:
-- tests/data/*.graphql
-- tests/data/*.min.graphql
-
 dependencies:
 - aeson
 - base >= 4.7 && < 5
diff --git a/src/Language/GraphQL/AST.hs b/src/Language/GraphQL/AST.hs
index 3d368d4..c7ceee8 100644
--- a/src/Language/GraphQL/AST.hs
+++ b/src/Language/GraphQL/AST.hs
@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 -- | Target AST for parser.
 module Language.GraphQL.AST
     ( module Language.GraphQL.AST.Document
diff --git a/src/Language/GraphQL/AST/DirectiveLocation.hs b/src/Language/GraphQL/AST/DirectiveLocation.hs
index 5b7a36f..c38c9ff 100644
--- a/src/Language/GraphQL/AST/DirectiveLocation.hs
+++ b/src/Language/GraphQL/AST/DirectiveLocation.hs
@@ -1,5 +1,9 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 -- | Various parts of a GraphQL document can be annotated with directives. 
---   This module describes locations in a document where directives can appear.
+-- This module describes locations in a document where directives can appear.
 module Language.GraphQL.AST.DirectiveLocation
     ( DirectiveLocation(..)
     , ExecutableDirectiveLocation(..)
@@ -7,8 +11,8 @@ module Language.GraphQL.AST.DirectiveLocation
     ) where
 
 -- | All directives can be splitted in two groups: directives used to annotate
---   various parts of executable definitions and the ones used in the schema
---   definition.
+-- various parts of executable definitions and the ones used in the schema
+-- definition.
 data DirectiveLocation
     = ExecutableDirectiveLocation ExecutableDirectiveLocation
     | TypeSystemDirectiveLocation TypeSystemDirectiveLocation
diff --git a/src/Language/GraphQL/Execute/Coerce.hs b/src/Language/GraphQL/Execute/Coerce.hs
index 60fb71d..08a2fc0 100644
--- a/src/Language/GraphQL/Execute/Coerce.hs
+++ b/src/Language/GraphQL/Execute/Coerce.hs
@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 {-# LANGUAGE ExplicitForAll #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE ViewPatterns #-}
diff --git a/src/Language/GraphQL/Type/In.hs b/src/Language/GraphQL/Type/In.hs
index 36e0e2c..8b08041 100644
--- a/src/Language/GraphQL/Type/In.hs
+++ b/src/Language/GraphQL/Type/In.hs
@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 {-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE ViewPatterns #-}
 
diff --git a/src/Language/GraphQL/Type/Schema.hs b/src/Language/GraphQL/Type/Schema.hs
index c5cc6fd..581d9b2 100644
--- a/src/Language/GraphQL/Type/Schema.hs
+++ b/src/Language/GraphQL/Type/Schema.hs
@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 -- | This module provides a representation of a @GraphQL@ Schema in addition to
 -- functions for defining and manipulating schemas.
 module Language.GraphQL.Type.Schema
diff --git a/src/Language/GraphQL/Validate/Rules.hs b/src/Language/GraphQL/Validate/Rules.hs
index a3314e7..9faaedd 100644
--- a/src/Language/GraphQL/Validate/Rules.hs
+++ b/src/Language/GraphQL/Validate/Rules.hs
@@ -17,7 +17,7 @@ import Language.GraphQL.AST.Document
 newtype Rule
     = DefinitionRule (Definition -> Maybe String)
 
--- | Default reules given in the specification.
+-- | Default rules given in the specification.
 specifiedRules :: [Rule]
 specifiedRules =
     [ executableDefinitionsRule
diff --git a/tests/Language/GraphQL/ErrorSpec.hs b/tests/Language/GraphQL/ErrorSpec.hs
index 482dc3a..1497c48 100644
--- a/tests/Language/GraphQL/ErrorSpec.hs
+++ b/tests/Language/GraphQL/ErrorSpec.hs
@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 {-# LANGUAGE OverloadedStrings #-}
 module Language.GraphQL.ErrorSpec
     ( spec
diff --git a/tests/Language/GraphQL/Execute/CoerceSpec.hs b/tests/Language/GraphQL/Execute/CoerceSpec.hs
index 339c2e3..2b00895 100644
--- a/tests/Language/GraphQL/Execute/CoerceSpec.hs
+++ b/tests/Language/GraphQL/Execute/CoerceSpec.hs
@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 {-# LANGUAGE OverloadedStrings #-}
 module Language.GraphQL.Execute.CoerceSpec
     ( spec
diff --git a/tests/Language/GraphQL/Type/OutSpec.hs b/tests/Language/GraphQL/Type/OutSpec.hs
index eecc374..733763d 100644
--- a/tests/Language/GraphQL/Type/OutSpec.hs
+++ b/tests/Language/GraphQL/Type/OutSpec.hs
@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 {-# LANGUAGE OverloadedStrings #-}
 module Language.GraphQL.Type.OutSpec
     ( spec
diff --git a/tests/Test/KitchenSinkSpec.hs b/tests/Test/KitchenSinkSpec.hs
deleted file mode 100644
index 9f5a947..0000000
--- a/tests/Test/KitchenSinkSpec.hs
+++ /dev/null
@@ -1,69 +0,0 @@
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE QuasiQuotes #-}
-module Test.KitchenSinkSpec
-    ( spec
-    ) where
-
-import qualified Data.Text.IO as Text.IO
-import qualified Data.Text.Lazy.IO as Text.Lazy.IO
-import qualified Data.Text.Lazy as Lazy (Text)
-import qualified Language.GraphQL.AST.Encoder as Encoder
-import qualified Language.GraphQL.AST.Parser as Parser
-import Paths_graphql (getDataFileName)
-import Test.Hspec (Spec, describe, it)
-import Test.Hspec.Megaparsec (parseSatisfies)
-import Text.Megaparsec (parse)
-import Text.RawString.QQ (r)
-
-spec :: Spec
-spec = describe "Kitchen Sink" $ do
-    it "minifies the query" $ do
-        dataFileName <- getDataFileName "tests/data/kitchen-sink.graphql"
-        minFileName <- getDataFileName "tests/data/kitchen-sink.min.graphql"
-        expected <- Text.Lazy.IO.readFile minFileName
-
-        shouldNormalize Encoder.minified dataFileName expected
-
-    it "pretty prints the query" $ do
-        dataFileName <- getDataFileName "tests/data/kitchen-sink.graphql"
-        let expected = [r|query queryName($foo: ComplexType, $site: Site = MOBILE) {
-  whoever123is: node(id: [123, 456]) {
-    id
-    ... on User @defer {
-      field2 {
-        id
-        alias: field1(first: 10, after: $foo) @include(if: $foo) {
-          id
-          ...frag
-        }
-      }
-    }
-  }
-}
-
-mutation likeStory {
-  like(story: 123) @defer {
-    story {
-      id
-    }
-  }
-}
-
-fragment frag on Friend {
-  foo(size: $size, bar: $b, obj: {key: "value"})
-}
-
-{
-  unnamed(truthy: true, falsey: false)
-  query
-}
-|]
-
-        shouldNormalize Encoder.pretty dataFileName expected
-
-shouldNormalize :: Encoder.Formatter -> FilePath -> Lazy.Text -> IO ()
-shouldNormalize formatter dataFileName expected = do
-    actual <- Text.IO.readFile dataFileName
-    parse Parser.document dataFileName actual `parseSatisfies` condition
-      where
-        condition = (expected ==) . Encoder.document formatter
diff --git a/tests/data/kitchen-sink.graphql b/tests/data/kitchen-sink.graphql
deleted file mode 100644
index 89903b7..0000000
--- a/tests/data/kitchen-sink.graphql
+++ /dev/null
@@ -1,38 +0,0 @@
-# Copyright (c) 2015, Facebook, Inc.
-# All rights reserved.
-#
-# This source code is licensed under the BSD-style license found in the
-# LICENSE file in the root directory of this source tree. An additional grant
-# of patent rights can be found in the PATENTS file in the same directory.
-
-query queryName($foo: ComplexType, $site: Site = MOBILE) {
-  whoever123is: node(id: [123, 456]) {
-    id, # Inline test comment
-    ... on User @defer {
-      field2 {
-        id,
-        alias: field1(first: 10, after: $foo) @include(if: $foo) {
-          id,
-          ...frag
-        }
-      }
-    }
-  }
-}
-
-mutation likeStory {
-  like(story: 123) @defer {
-    story {
-      id
-    }
-  }
-}
-
-fragment frag on Friend {
-  foo(size: $size, bar: $b, obj: {key: "value"})
-}
-
-{
-  unnamed(truthy: true, falsey: false),
-  query
-}
diff --git a/tests/data/kitchen-sink.min.graphql b/tests/data/kitchen-sink.min.graphql
deleted file mode 100644
index 24f5c26..0000000
--- a/tests/data/kitchen-sink.min.graphql
+++ /dev/null
@@ -1 +0,0 @@
-query queryName($foo:ComplexType,$site:Site=MOBILE){whoever123is:node(id:[123,456]){id,... on User@defer{field2{id,alias:field1(first:10,after:$foo)@include(if:$foo){id,...frag}}}}}mutation likeStory{like(story:123)@defer{story{id}}}fragment frag on Friend{foo(size:$size,bar:$b,obj:{key:"value"})}{unnamed(truthy:true,falsey:false),query}