diff --git a/.github/workflows/dart.yml b/.github/workflows/dart.yml
index f8c2d35..0297fc1 100644
--- a/.github/workflows/dart.yml
+++ b/.github/workflows/dart.yml
@@ -25,4 +25,4 @@ jobs:
       - name: Tests
         run: dart test --coverage=.coverage -j1
       - name: Coverage
-        run: dart run coverage:format_coverage -l -c -i .coverage --report-on=lib | dart run check_coverage:check_coverage 98
+        run: dart run coverage:format_coverage -l -c -i .coverage --report-on=lib | dart run check_coverage:check_coverage
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
new file mode 100644
index 0000000..d79d8c8
--- /dev/null
+++ b/.github/workflows/publish.yml
@@ -0,0 +1,14 @@
+name: Publish to pub.dev
+
+on:
+  push:
+    tags:
+      - '[0-9]+.[0-9]+.[0-9]+*'
+
+jobs:
+  publish:
+    permissions:
+      id-token: write # Required for authentication using OIDC
+    uses: dart-lang/setup-dart/.github/workflows/publish.yml@v1
+    # with:
+    #   working-directory: path/to/package/within/repository
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0707da2..679d663 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [7.0.0] - 2023-11-12
+### Changed
+- Migrated to `http_interop` v1.
+
 ## [6.0.1] - 2023-09-11
 ### Fixed
 - `NewRelationship` was not exported
@@ -242,6 +246,7 @@ the Document model.
 ### Added
 - Client: fetch resources, collections, related resources and relationships
 
+[7.0.0]: https://github.com/f3ath/json-api-dart/compare/6.0.1...7.0.0
 [6.0.1]: https://github.com/f3ath/json-api-dart/compare/6.0.0...6.0.1
 [6.0.0]: https://github.com/f3ath/json-api-dart/compare/5.4.0...6.0.0
 [5.4.0]: https://github.com/f3ath/json-api-dart/compare/5.3.0...5.4.0
diff --git a/example/server.dart b/example/server.dart
index 57dccb9..bea19e0 100644
--- a/example/server.dart
+++ b/example/server.dart
@@ -22,11 +22,11 @@ Future<void> main() async {
       ControllerRouter(controller, StandardUriDesign.matchTarget);
   handler = TryCatchHandler(handler,
       onError: ErrorConverter(onError: (e, stack) async {
-    stderr.writeln(e);
-    return Response(500,
-        document: OutboundErrorDocument(
-            [ErrorObject(title: 'Internal Server Error')]));
-  }));
+        stderr.writeln(e);
+        return Response(500,
+            document: OutboundErrorDocument(
+                [ErrorObject(title: 'Internal Server Error')]));
+      }).call);
   handler = LoggingHandler(handler,
       onRequest: (r) => print('${r.method} ${r.uri}'),
       onResponse: (r) => print('${r.statusCode}'));
diff --git a/example/server/cors_handler.dart b/example/server/cors_handler.dart
index c419a0a..073ee0d 100644
--- a/example/server/cors_handler.dart
+++ b/example/server/cors_handler.dart
@@ -13,12 +13,12 @@ class CorsHandler implements Handler {
       'Access-Control-Expose-Headers': ['Location'],
     };
 
-    if (request.method.equals('OPTIONS')) {
+    if (request.method == 'options') {
       const methods = ['POST', 'GET', 'DELETE', 'PATCH', 'OPTIONS'];
       return Response(
           204,
-          Body.empty(),
-          Headers({
+          Body(),
+          Headers.from({
             ...headers,
             'Access-Control-Allow-Methods':
                 request.headers['Access-Control-Request-Method'] ?? methods,
diff --git a/lib/http.dart b/lib/http.dart
index 0cd26e6..5a190c6 100644
--- a/lib/http.dart
+++ b/lib/http.dart
@@ -1,5 +1,3 @@
-import 'dart:convert';
-
 import 'package:http_interop/http_interop.dart';
 
 class StatusCode {
@@ -29,7 +27,7 @@ class StatusCode {
 }
 
 class Json extends Body {
-  Json(Map<String, Object?> json) : super(jsonEncode(json), utf8);
+  Json(Map<String, Object?> super.object) : super.json();
 }
 
 class LoggingHandler implements Handler {
diff --git a/lib/src/client/client.dart b/lib/src/client/client.dart
index 083f05d..405267e 100644
--- a/lib/src/client/client.dart
+++ b/lib/src/client/client.dart
@@ -23,8 +23,8 @@ class Client {
   /// Sends the [request] to the given [uri].
   Future<Response> send(Uri uri, Request request) async {
     final json = await _encode(request.document);
-    final body = http.Body(json, utf8);
-    final headers = http.Headers({
+    final body = http.Body.text(json, utf8);
+    final headers = http.Headers.from({
       'Accept': [mediaType],
       if (json.isNotEmpty) 'Content-Type': [mediaType],
       ...request.headers
@@ -32,8 +32,8 @@ class Client {
     final url = request.query.isEmpty
         ? uri
         : uri.replace(queryParameters: request.query.toQuery());
-    final response = await _handler
-        .handle(http.Request(http.Method(request.method), url, body, headers));
+    final response =
+        await _handler.handle(http.Request(request.method, url, body, headers));
 
     final document = await _decode(response);
     return Response(response, document);
diff --git a/lib/src/client/request.dart b/lib/src/client/request.dart
index d2f30bf..0046727 100644
--- a/lib/src/client/request.dart
+++ b/lib/src/client/request.dart
@@ -31,5 +31,5 @@ class Request {
   final query = Query();
 
   /// HTTP headers.
-  final headers = Headers({});
+  final headers = Headers();
 }
diff --git a/lib/src/document/inbound_document.dart b/lib/src/document/inbound_document.dart
index 962052a..4571c69 100644
--- a/lib/src/document/inbound_document.dart
+++ b/lib/src/document/inbound_document.dart
@@ -147,13 +147,11 @@ class _Parser {
 
   /// Decodes Link from [json]. Returns the decoded object.
   /// If the [json] has incorrect format, throws  [FormatException].
-  Link _link(Object json) {
-    if (json is String) return Link(Uri.parse(json));
-    if (json is Map) {
-      return Link(Uri.parse(json['href']))..meta.addAll(meta(json));
-    }
-    throw FormatException('Invalid JSON');
-  }
+  Link _link(Object json) => switch (json) {
+        String() => Link(Uri.parse(json)),
+        Map() => Link(Uri.parse(json['href']))..meta.addAll(meta(json)),
+        _ => throw FormatException('Invalid JSON')
+      };
 
   Map<String, Object?> _getAttributes(Map json) =>
       json.get<Map<String, Object?>>('attributes', orGet: () => {});
@@ -166,25 +164,19 @@ class _Parser {
       .get<Map>('relationships', orGet: () => {})
       .map((key, value) => MapEntry(key, newRelationship(value)));
 
-  Relationship _rel(data) {
-    if (data == null) return ToOne.empty();
-    if (data is Map) return ToOne(identifier(data));
-    if (data is List) return ToMany(data.whereType<Map>().map(identifier));
-    throw FormatException('Invalid relationship object');
-  }
-
-  NewRelationship _newRel(data) {
-    if (data == null) {
-      return NewToOne.empty();
-    }
-    if (data is Map) {
-      return NewToOne(newIdentifier(data));
-    }
-    if (data is List) {
-      return NewToMany(data.whereType<Map>().map(newIdentifier));
-    }
-    throw FormatException('Invalid relationship object');
-  }
+  Relationship _rel(data) => switch (data) {
+        null => ToOne.empty(),
+        Map() => ToOne(identifier(data)),
+        List() => ToMany(data.whereType<Map>().map(identifier)),
+        _ => throw FormatException('Invalid relationship object')
+      };
+
+  NewRelationship _newRel(data) => switch (data) {
+        null => NewToOne.empty(),
+        Map() => NewToOne(newIdentifier(data)),
+        List() => NewToMany(data.whereType<Map>().map(newIdentifier)),
+        _ => throw FormatException('Invalid relationship object')
+      };
 }
 
 extension _TypedGeter on Map {
diff --git a/lib/src/document/new_relationship.dart b/lib/src/document/new_relationship.dart
index f985ea0..65de471 100644
--- a/lib/src/document/new_relationship.dart
+++ b/lib/src/document/new_relationship.dart
@@ -12,8 +12,6 @@ class NewRelationship with IterableMixin<NewIdentifier> {
         if (meta.isNotEmpty) 'meta': meta,
       };
 
-  // coverage:ignore-start
   @override
   Iterator<NewIdentifier> get iterator => <NewIdentifier>[].iterator;
-// coverage:ignore-end
 }
diff --git a/lib/src/document/new_resource.dart b/lib/src/document/new_resource.dart
index b111ab7..3cf4be7 100644
--- a/lib/src/document/new_resource.dart
+++ b/lib/src/document/new_resource.dart
@@ -61,7 +61,6 @@ class NewResource {
     if (r is NewToMany) {
       return ToMany(r.map((identifier) => _toIdentifier(identifier, id)));
     }
-    // coverage:ignore-line
     throw StateError('Unexpected relationship type: ${r.runtimeType}');
   }
 
@@ -70,16 +69,12 @@ class NewResource {
     return _toIdentifier(identifier, id);
   }
 
-  Identifier _toIdentifier(NewIdentifier identifier, String id) {
-    switch (identifier) {
-      case Identifier():
-        return identifier;
-      case LocalIdentifier():
-        if (identifier.type == type && identifier.lid == lid) {
-          return identifier.toIdentifier(id);
-        }
-        throw StateError(
-            'Unmatched local id: "${identifier.lid}". Expected "$lid".');
-    }
-  }
+  Identifier _toIdentifier(NewIdentifier identifier, String id) =>
+      switch (identifier) {
+        Identifier() => identifier,
+        LocalIdentifier() => (identifier.type == type && identifier.lid == lid)
+            ? identifier.toIdentifier(id)
+            : throw StateError(
+                'Unmatched local id: "${identifier.lid}". Expected "$lid".')
+      };
 }
diff --git a/lib/src/routing/standard_uri_design.dart b/lib/src/routing/standard_uri_design.dart
index 27d1382..2b474f6 100644
--- a/lib/src/routing/standard_uri_design.dart
+++ b/lib/src/routing/standard_uri_design.dart
@@ -11,22 +11,14 @@ class StandardUriDesign implements UriDesign {
   /// `/books`, `/books/42`, `/books/42/authors`
   static final pathOnly = StandardUriDesign(Uri(path: '/'));
 
-  static Target? matchTarget(Uri uri) {
-    final s = uri.pathSegments;
-    if (s.length == 1) {
-      return Target(s.first);
-    }
-    if (s.length == 2) {
-      return ResourceTarget(s.first, s.last);
-    }
-    if (s.length == 3) {
-      return RelatedTarget(s.first, s[1], s.last);
-    }
-    if (s.length == 4 && s[2] == 'relationships') {
-      return RelationshipTarget(s.first, s[1], s.last);
-    }
-    return null;
-  }
+  static Target? matchTarget(Uri uri) => switch ((uri.pathSegments)) {
+        [var type] => Target(type),
+        [var type, var id] => ResourceTarget(type, id),
+        [var type, var id, var rel] => RelatedTarget(type, id, rel),
+        [var type, var id, 'relationships', var rel] =>
+          RelationshipTarget(type, id, rel),
+        _ => null
+      };
 
   final Uri base;
 
diff --git a/lib/src/server/controller_router.dart b/lib/src/server/controller_router.dart
index 3f45e37..08f25a6 100644
--- a/lib/src/server/controller_router.dart
+++ b/lib/src/server/controller_router.dart
@@ -18,49 +18,31 @@ class ControllerRouter implements Handler {
   Future<Response> handle(Request request) async {
     _validate(request);
     final target = _matchTarget(request.uri);
-    if (target is RelationshipTarget) {
-      if (request.method.equals('GET')) {
-        return await _controller.fetchRelationship(request, target);
-      }
-      if (request.method.equals('POST')) {
-        return await _controller.addMany(request, target);
-      }
-      if (request.method.equals('PATCH')) {
-        return await _controller.replaceRelationship(request, target);
-      }
-      if (request.method.equals('DELETE')) {
-        return await _controller.deleteMany(request, target);
-      }
-      throw MethodNotAllowed(request.method.value);
-    }
-    if (target is RelatedTarget) {
-      if (request.method.equals('GET')) {
-        return await _controller.fetchRelated(request, target);
-      }
-      throw MethodNotAllowed(request.method.value);
-    }
-    if (target is ResourceTarget) {
-      if (request.method.equals('GET')) {
-        return await _controller.fetchResource(request, target);
-      }
-      if (request.method.equals('PATCH')) {
-        return await _controller.updateResource(request, target);
-      }
-      if (request.method.equals('DELETE')) {
-        return await _controller.deleteResource(request, target);
-      }
-      throw MethodNotAllowed(request.method.value);
-    }
-    if (target is Target) {
-      if (request.method.equals('GET')) {
-        return await _controller.fetchCollection(request, target);
-      }
-      if (request.method.equals('POST')) {
-        return await _controller.createResource(request, target);
-      }
-      throw MethodNotAllowed(request.method.value);
-    }
-    throw UnmatchedTarget(request.uri);
+    return await switch (target) {
+      RelationshipTarget() => switch (request.method) {
+          'get' => _controller.fetchRelationship(request, target),
+          'post' => _controller.addMany(request, target),
+          'patch' => _controller.replaceRelationship(request, target),
+          'delete' => _controller.deleteMany(request, target),
+          _ => throw MethodNotAllowed(request.method)
+        },
+      RelatedTarget() => switch (request.method) {
+          'get' => _controller.fetchRelated(request, target),
+          _ => throw MethodNotAllowed(request.method)
+        },
+      ResourceTarget() => switch (request.method) {
+          'get' => _controller.fetchResource(request, target),
+          'patch' => _controller.updateResource(request, target),
+          'delete' => _controller.deleteResource(request, target),
+          _ => throw MethodNotAllowed(request.method)
+        },
+      Target() => switch (request.method) {
+          'get' => _controller.fetchCollection(request, target),
+          'post' => _controller.createResource(request, target),
+          _ => throw MethodNotAllowed(request.method)
+        },
+      _ => throw UnmatchedTarget(request.uri)
+    };
   }
 
   void _validate(Request request) {
diff --git a/lib/src/server/response.dart b/lib/src/server/response.dart
index b15084c..d8cabaa 100644
--- a/lib/src/server/response.dart
+++ b/lib/src/server/response.dart
@@ -1,5 +1,3 @@
-import 'dart:convert';
-
 import 'package:http_interop/http_interop.dart' as http;
 import 'package:json_api/document.dart';
 import 'package:json_api/http.dart';
@@ -10,10 +8,8 @@ class Response<D extends OutboundDocument> extends http.Response {
   Response(int statusCode, {D? document})
       : super(
             statusCode,
-            document != null
-                ? http.Body(jsonEncode(document), utf8)
-                : http.Body.empty(),
-            http.Headers({})) {
+            document != null ? http.Body.json(document) : http.Body(),
+            http.Headers()) {
     if (document != null) {
       headers['Content-Type'] = [mediaType];
     }
diff --git a/pubspec.yaml b/pubspec.yaml
index f93f095..d47cfb3 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,24 +1,24 @@
 name: json_api
-version: 6.0.1
+version: 7.0.0
 homepage: https://github.com/f3ath/json-api-dart
 description: A framework-agnostic implementations of JSON:API Client and Server. Supports JSON:API v1.0 (https://jsonapi.org)
 environment:
-  sdk: '>=3.0.0 <4.0.0'
+  sdk: '>=3.1.0 <4.0.0'
 
 dependencies:
   http_parser: ^4.0.0
-  http_interop: ^0.8.0
+  http_interop: ^1.0.0
 
 dev_dependencies:
-  lints: ^2.1.1
+  lints: ^3.0.0
   test: ^1.21.1
   stream_channel: ^2.1.0
-  uuid: ^3.0.0
+  uuid: ^4.2.0
   coverage: ^1.3.0
   check_coverage: ^0.0.4
   http: ^1.1.0
-  http_interop_http: ^0.6.0
-  http_interop_io: ^0.6.0
+  http_interop_http: ^0.7.0
+  http_interop_io: ^0.7.0
 
 
 cider:
diff --git a/test/contract/errors_test.dart b/test/contract/errors_test.dart
index db60cff..edccf8b 100644
--- a/test/contract/errors_test.dart
+++ b/test/contract/errors_test.dart
@@ -26,16 +26,16 @@ void main() {
       }
     });
     test('Bad request when target can not be matched', () async {
-      final r = await TestHandler().handle(http.Request(http.Method('get'),
-          Uri.parse('/a/long/prefix/'), http.Body.empty(), http.Headers({})));
+      final r = await TestHandler().handle(http.Request(
+          'get', Uri.parse('/a/long/prefix/'), http.Body(), http.Headers()));
       expect(r.statusCode, 400);
     });
     test('Unsupported extension', () async {
       final r = await TestHandler().handle(http.Request(
-          http.Method('get'),
+          'get',
           Uri.parse('/posts/1'),
-          http.Body.empty(),
-          http.Headers({
+          http.Body(),
+          http.Headers.from({
             'Content-Type': ['application/vnd.api+json; ext=foobar'],
             'Accept': ['application/vnd.api+json']
           })));
@@ -43,10 +43,10 @@ void main() {
     });
     test('Unacceptable', () async {
       final r = await TestHandler().handle(http.Request(
-          http.Method('get'),
+          'get',
           Uri.parse('/posts/1'),
-          http.Body.empty(),
-          http.Headers({
+          http.Body(),
+          http.Headers.from({
             'Content-Type': ['application/vnd.api+json'],
             'Accept': ['application/vnd.api+json; ext=foobar']
           })));
diff --git a/test/test_handler.dart b/test/test_handler.dart
index d26214e..3b29817 100644
--- a/test/test_handler.dart
+++ b/test/test_handler.dart
@@ -17,11 +17,12 @@ class TestHandler extends LoggingHandler {
                 ControllerRouter(RepositoryController(InMemoryRepo(types), _id),
                     StandardUriDesign.matchTarget),
                 onError: ErrorConverter(
-                    onError: onError ??
-                        (err, trace) {
-                          print(trace);
-                          throw err;
-                        })),
+                        onError: onError ??
+                            (err, trace) {
+                              print(trace);
+                              throw err;
+                            })
+                    .call),
             onRequest: onRequest,
             onResponse: onResponse);
 }
diff --git a/test/unit/client/client_test.dart b/test/unit/client/client_test.dart
index 6fe5120..c617682 100644
--- a/test/unit/client/client_test.dart
+++ b/test/unit/client/client_test.dart
@@ -44,7 +44,7 @@ void main() {
       expect(response.collection.single.type, 'articles');
       expect(response.collection.single.id, '1');
       expect(response.included, isEmpty);
-      expect(http.request.method.value, 'get');
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.toString(), '/articles');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json']
@@ -70,7 +70,7 @@ void main() {
 
     expect(response.collection.length, 1);
     expect(response.included.length, 3);
-    expect(http.request.method.value, 'get');
+    expect(http.request.method, equals('get'));
     expect(http.request.uri.path, '/articles');
     expect(http.request.uri.queryParameters, {
       'include': 'author',
@@ -93,7 +93,7 @@ void main() {
       final response =
           await client.fetchRelatedCollection('people', '1', 'articles');
       expect(response.collection.length, 1);
-      expect(http.request.method.equals('get'), true);
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.path, '/people/1/articles');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json']
@@ -119,7 +119,7 @@ void main() {
 
       expect(response.collection.length, 1);
       expect(response.included.length, 3);
-      expect(http.request.method.equals('get'), true);
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.path, '/people/1/articles');
       expect(http.request.uri.queryParameters, {
         'include': 'author',
@@ -142,7 +142,7 @@ void main() {
       http.response = mock.primaryResource();
       final response = await client.fetchResource('articles', '1');
       expect(response.resource.type, 'articles');
-      expect(http.request.method.equals('get'), true);
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.toString(), '/articles/1');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json']
@@ -164,7 +164,7 @@ void main() {
       ]);
       expect(response.resource.type, 'articles');
       expect(response.included.length, 3);
-      expect(http.request.method.equals('get'), true);
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.path, '/articles/1');
       expect(http.request.uri.queryParameters,
           {'include': 'author', 'fields[author]': 'name', 'foo': 'bar'});
@@ -184,7 +184,7 @@ void main() {
           await client.fetchRelatedResource('articles', '1', 'author');
       expect(response.resource?.type, 'articles');
       expect(response.included.length, 3);
-      expect(http.request.method.equals('get'), true);
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.toString(), '/articles/1/author');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json']
@@ -207,7 +207,7 @@ void main() {
       ]);
       expect(response.resource?.type, 'articles');
       expect(response.included.length, 3);
-      expect(http.request.method.equals('get'), true);
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.path, '/articles/1/author');
       expect(http.request.uri.queryParameters,
           {'include': 'author', 'fields[author]': 'name', 'foo': 'bar'});
@@ -225,7 +225,7 @@ void main() {
           await client.fetchRelatedResource('articles', '1', 'author');
       expect(response.resource, isNull);
       expect(response.included, isEmpty);
-      expect(http.request.method.equals('get'), true);
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.toString(), '/articles/1/author');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json']
@@ -238,7 +238,7 @@ void main() {
       http.response = mock.one();
       final response = await client.fetchToOne('articles', '1', 'author');
       expect(response.included.length, 3);
-      expect(http.request.method.equals('get'), true);
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.toString(), '/articles/1/relationships/author');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json']
@@ -256,7 +256,7 @@ void main() {
         })
       ]);
       expect(response.included.length, 3);
-      expect(http.request.method.equals('get'), true);
+      expect(http.request.method, equals('get'));
       expect(http.request.uri.path, '/articles/1/relationships/author');
       expect(http.request.uri.queryParameters, {'foo': 'bar'});
       expect(http.request.headers, {
@@ -274,7 +274,7 @@ void main() {
       expect(
           response.links['self'].toString(), 'http://example.com/articles/1');
       expect(response.included.length, 3);
-      expect(http.request.method.equals('post'), true);
+      expect(http.request.method, equals('post'));
       expect(http.request.uri.toString(), '/articles');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -304,7 +304,7 @@ void main() {
       expect(
           response.links['self'].toString(), 'http://example.com/articles/1');
       expect(response.included.length, 3);
-      expect(http.request.method.equals('post'), true);
+      expect(http.request.method, equals('post'));
       expect(http.request.uri.toString(), '/articles');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -344,7 +344,7 @@ void main() {
       http.response = mock.primaryResource();
       final response = await client.create('articles', '1');
       expect(response.resource?.type, 'articles');
-      expect(http.request.method.equals('post'), true);
+      expect(http.request.method, equals('post'));
       expect(http.request.uri.toString(), '/articles');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -359,7 +359,7 @@ void main() {
       http.response = mock.noContent();
       final response = await client.create('articles', '1');
       expect(response.resource, isNull);
-      expect(http.request.method.equals('post'), true);
+      expect(http.request.method, equals('post'));
       expect(http.request.uri.toString(), '/articles');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -386,7 +386,7 @@ void main() {
         'foo': ['bar']
       });
       expect(response.resource?.type, 'articles');
-      expect(http.request.method.equals('post'), true);
+      expect(http.request.method, equals('post'));
       expect(http.request.uri.toString(), '/articles');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -427,7 +427,7 @@ void main() {
       http.response = mock.primaryResource();
       final response = await client.updateResource('articles', '1');
       expect(response.resource?.type, 'articles');
-      expect(http.request.method.equals('patch'), true);
+      expect(http.request.method, equals('patch'));
       expect(http.request.uri.toString(), '/articles/1');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -442,7 +442,7 @@ void main() {
       http.response = mock.noContent();
       final response = await client.updateResource('articles', '1');
       expect(response.resource, isNull);
-      expect(http.request.method.equals('patch'), true);
+      expect(http.request.method, equals('patch'));
       expect(http.request.uri.toString(), '/articles/1');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -470,7 +470,7 @@ void main() {
         'foo': ['bar']
       });
       expect(response.resource?.type, 'articles');
-      expect(http.request.method.equals('patch'), true);
+      expect(http.request.method, equals('patch'));
       expect(http.request.uri.toString(), '/articles/1');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -512,7 +512,7 @@ void main() {
       final response = await client.replaceToOne(
           'articles', '1', 'author', Identifier('people', '42'));
       expect(response.relationship, isA<ToOne>());
-      expect(http.request.method.equals('patch'), true);
+      expect(http.request.method, equals('patch'));
       expect(http.request.uri.toString(), '/articles/1/relationships/author');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -534,7 +534,7 @@ void main() {
             'foo': ['bar']
           });
       expect(response.relationship, isA<ToOne>());
-      expect(http.request.method.equals('patch'), true);
+      expect(http.request.method, equals('patch'));
       expect(http.request.uri.toString(), '/articles/1/relationships/author');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -574,7 +574,7 @@ void main() {
       final response = await client.deleteToOne('articles', '1', 'author');
       expect(response.relationship, isA<ToOne>());
       expect(response.relationship!.identifier, isNull);
-      expect(http.request.method.equals('patch'), true);
+      expect(http.request.method, equals('patch'));
       expect(http.request.uri.toString(), '/articles/1/relationships/author');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -591,7 +591,7 @@ void main() {
       });
       expect(response.relationship, isA<ToOne>());
       expect(response.relationship!.identifier, isNull);
-      expect(http.request.method.equals('patch'), true);
+      expect(http.request.method, equals('patch'));
       expect(http.request.uri.toString(), '/articles/1/relationships/author');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -625,7 +625,7 @@ void main() {
       final response = await client
           .deleteFromMany('articles', '1', 'tags', [Identifier('tags', '1')]);
       expect(response.relationship, isA<ToMany>());
-      expect(http.request.method.equals('delete'), true);
+      expect(http.request.method, equals('delete'));
       expect(http.request.uri.toString(), '/articles/1/relationships/tags');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -648,7 +648,7 @@ void main() {
         'foo': ['bar']
       });
       expect(response.relationship, isA<ToMany>());
-      expect(http.request.method.equals('delete'), true);
+      expect(http.request.method, equals('delete'));
       expect(http.request.uri.toString(), '/articles/1/relationships/tags');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -690,7 +690,7 @@ void main() {
       final response = await client
           .replaceToMany('articles', '1', 'tags', [Identifier('tags', '1')]);
       expect(response.relationship, isA<ToMany>());
-      expect(http.request.method.equals('patch'), true);
+      expect(http.request.method, equals('patch'));
       expect(http.request.uri.toString(), '/articles/1/relationships/tags');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -713,7 +713,7 @@ void main() {
         'foo': ['bar']
       });
       expect(response.relationship, isA<ToMany>());
-      expect(http.request.method.equals('patch'), true);
+      expect(http.request.method, equals('patch'));
       expect(http.request.uri.toString(), '/articles/1/relationships/tags');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -755,7 +755,7 @@ void main() {
       final response = await client
           .addMany('articles', '1', 'tags', [Identifier('tags', '1')]);
       expect(response.relationship, isA<ToMany>());
-      expect(http.request.method.equals('post'), true);
+      expect(http.request.method, equals('post'));
       expect(http.request.uri.toString(), '/articles/1/relationships/tags');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
@@ -778,7 +778,7 @@ void main() {
         'foo': ['bar']
       });
       expect(response.relationship, isA<ToMany>());
-      expect(http.request.method.equals('post'), true);
+      expect(http.request.method, equals('post'));
       expect(http.request.uri.toString(), '/articles/1/relationships/tags');
       expect(http.request.headers, {
         'Accept': ['application/vnd.api+json'],
diff --git a/test/unit/client/response.dart b/test/unit/client/response.dart
index ce1c81e..1a64603 100644
--- a/test/unit/client/response.dart
+++ b/test/unit/client/response.dart
@@ -2,7 +2,7 @@ import 'package:http_interop/http_interop.dart';
 import 'package:json_api/http.dart';
 import 'package:json_api/src/media_type.dart';
 
-final headers = Headers({
+final headers = Headers.from({
   'Content-Type': [mediaType]
 });
 
@@ -255,7 +255,7 @@ many() => Response(
     }),
     headers);
 
-noContent() => Response(204, Body.empty(), Headers({}));
+noContent() => Response(204, Body(), Headers());
 
 error422() => Response(
     422,
@@ -272,4 +272,4 @@ error422() => Response(
     }),
     headers);
 
-error500() => Response(500, Body.empty(), Headers({}));
+error500() => Response(500, Body(), Headers());
diff --git a/test/unit/document/inbound_document_test.dart b/test/unit/document/inbound_document_test.dart
index 0123e38..d5b4c22 100644
--- a/test/unit/document/inbound_document_test.dart
+++ b/test/unit/document/inbound_document_test.dart
@@ -188,6 +188,20 @@ void main() {
         expect(() => InboundDocument(payload.many).asToOne(),
             throwsFormatException);
       });
+
+      test('throws on invalid new relationship', () {
+        expect(
+            () => InboundDocument(payload.newResourceInvalidRelationship)
+                .dataAsNewResource(),
+            throwsFormatException);
+      });
+
+      test('throws on incomplete new relationship', () {
+        expect(
+            () => InboundDocument(payload.newResourceIncompleteRelationship)
+                .dataAsNewResource(),
+            throwsFormatException);
+      });
     });
   });
 }
diff --git a/test/unit/document/new_relationship_test.dart b/test/unit/document/new_relationship_test.dart
new file mode 100644
index 0000000..504d442
--- /dev/null
+++ b/test/unit/document/new_relationship_test.dart
@@ -0,0 +1,13 @@
+import 'package:json_api/document.dart';
+import 'package:test/expect.dart';
+import 'package:test/scaffolding.dart';
+
+void main() {
+  group('NewRelationship', () {
+    test('iterator', () {
+      final list = [];
+      list.addAll(NewRelationship());
+      expect(list, isEmpty);
+    });
+  });
+}
diff --git a/test/unit/document/new_resource_test.dart b/test/unit/document/new_resource_test.dart
index 1e0cd9d..eba069e 100644
--- a/test/unit/document/new_resource_test.dart
+++ b/test/unit/document/new_resource_test.dart
@@ -5,6 +5,30 @@ import 'package:test/test.dart';
 
 void main() {
   group('NewResource', () {
+    test('toResource throws on unmatched local id in "many"', () {
+      final resource = NewResource('test_type', id: 'test_id', lid: 'test_lid')
+        ..relationships['many'] = NewToMany([
+          LocalIdentifier('test_type', 'test_lid2'),
+        ]);
+
+      expect(() => resource.toResource(() => 'my-test-id'), throwsStateError);
+    });
+
+    test('toResource throws on unmatched local id in "one"', () {
+      final resource = NewResource('test_type', id: 'test_id', lid: 'test_lid')
+        ..relationships['one'] =
+            NewToOne(LocalIdentifier('test_type', 'test_lid2'));
+
+      expect(() => resource.toResource(() => 'my-test-id'), throwsStateError);
+    });
+
+    test('toResource throws on invalid relationship', () {
+      final resource = NewResource('test_type', id: 'test_id')
+        ..relationships['many'] = NewRelationship();
+
+      expect(() => resource.toResource(() => 'my-test-id'), throwsStateError);
+    });
+
     test('json encoding', () {
       expect(jsonEncode(NewResource('test_type')),
           jsonEncode({'type': 'test_type'}));
diff --git a/test/unit/document/new_to_one_test.dart b/test/unit/document/new_to_one_test.dart
new file mode 100644
index 0000000..6853d3a
--- /dev/null
+++ b/test/unit/document/new_to_one_test.dart
@@ -0,0 +1,15 @@
+import 'package:json_api/document.dart';
+import 'package:test/expect.dart';
+import 'package:test/scaffolding.dart';
+
+void main() {
+  group('NewToOne', () {
+    test('can be iterated', () {
+      final id = Identifier('books', '123');
+      final r = NewToOne(id);
+      final list = <NewIdentifier>[];
+      list.addAll(r);
+      expect(list.single, equals(id));
+    });
+  });
+}
diff --git a/test/unit/document/payload.dart b/test/unit/document/payload.dart
index c7d6cb0..9653ac3 100644
--- a/test/unit/document/payload.dart
+++ b/test/unit/document/payload.dart
@@ -147,3 +147,27 @@ final resource = {
     }
   }
 };
+
+final newResourceInvalidRelationship = {
+  'data': {
+    'type': 'articles',
+    'attributes': {'title': 'JSON:API paints my bikeshed!'},
+    'relationships': {
+      'author': {
+        'data': true,
+      },
+    }
+  }
+};
+
+final newResourceIncompleteRelationship = {
+  'data': {
+    'type': 'articles',
+    'attributes': {'title': 'JSON:API paints my bikeshed!'},
+    'relationships': {
+      'author': {
+        'data': {'type': 'person'},
+      },
+    }
+  }
+};