diff --git a/flask/testing.py b/flask/testing.py
index 8eacf58b..dd879c37 100644
--- a/flask/testing.py
+++ b/flask/testing.py
@@ -13,6 +13,7 @@
 from contextlib import contextmanager
 from werkzeug.test import Client, EnvironBuilder
 from flask import _request_ctx_stack
+from flask.json import dumps as json_dumps
 
 try:
     from werkzeug.urls import url_parse
@@ -20,7 +21,7 @@ except ImportError:
     from urlparse import urlsplit as url_parse
 
 
-def make_test_environ_builder(app, path='/', base_url=None, *args, **kwargs):
+def make_test_environ_builder(app, path='/', base_url=None, json=None, *args, **kwargs):
     """Creates a new test builder with some application defaults thrown in."""
     http_host = app.config.get('SERVER_NAME')
     app_root = app.config.get('APPLICATION_ROOT')
@@ -33,6 +34,18 @@ def make_test_environ_builder(app, path='/', base_url=None, *args, **kwargs):
             path = url.path
             if url.query:
                 path += '?' + url.query
+
+    if json:
+        if 'data' in kwargs:
+            raise RuntimeError('Client cannot provide both `json` and `data`')
+        kwargs['data'] = json_dumps(json)
+
+        # Only set Content-Type when not explicitly provided
+        if 'Content-Type' not in kwargs.get('headers', {}):
+            new_headers = kwargs.get('headers', {}).copy()
+            new_headers['Content-Type'] = 'application/json'
+            kwargs['headers'] = new_headers
+
     return EnvironBuilder(path, base_url, *args, **kwargs)
 
 
diff --git a/tests/test_testing.py b/tests/test_testing.py
index 7bb99e79..b3f4defe 100644
--- a/tests/test_testing.py
+++ b/tests/test_testing.py
@@ -203,6 +203,20 @@ def test_full_url_request():
         assert 'gin' in flask.request.form
         assert 'vodka' in flask.request.args
 
+def test_json_request():
+    app = flask.Flask(__name__)
+    app.testing = True
+
+    @app.route('/api', methods=['POST'])
+    def api():
+        return ''
+
+    with app.test_client() as c:
+        json_data = {'drink': {'gin': 1, 'tonic': True}, 'price': 10}
+        rv = c.post('/api', json=json_data)
+        assert rv.status_code == 200
+        assert flask.request.get_json() == json_data
+
 def test_subdomain():
     app = flask.Flask(__name__)
     app.config['SERVER_NAME'] = 'example.com'