DRYing up the test suite using pytest fixtures (#2306)

* add fixtures to conftest.py

* use fixtures in test_appctx.py

* use fixtures in test_blueprints.py

* use fixtures in test_depreciations.py

* use fixtures in test_regressions.py

* use fixtures in test_reqctx.py

* use fixtures in test_templating.py

* use fixtures in test_user_error_handler.py

* use fixtures in test_views.py

* use fixtures in test_basics.py

* use fixtures in test_helpers.py

* use fixtures in test_testing.py

* update conftest.py

* make docstrings  PEP-257 compliant

* cleanup

* switch dictonary format

* use pytest parameterization for test_json_as_unicode

tests/test_user_error_handler.py

@@ -8,8 +8,7 @@ from werkzeug.exceptions import (
 import flask
 
 
-def test_error_handler_no_match():
-    app = flask.Flask(__name__)
+def test_error_handler_no_match(app, client):
 
     class CustomException(Exception):
         pass
@@ -31,15 +30,12 @@ def test_error_handler_no_match():
     def key_error():
         raise KeyError()
 
-    c = app.test_client()
-
-    assert c.get('/custom').data == b'custom'
-    assert c.get('/keyerror').data == b'KeyError'
+    app.testing = False
+    assert client.get('/custom').data == b'custom'
+    assert client.get('/keyerror').data == b'KeyError'
 
 
-def test_error_handler_subclass():
-    app = flask.Flask(__name__)
-
+def test_error_handler_subclass(app):
     class ParentException(Exception):
         pass
 
@@ -78,9 +74,7 @@ def test_error_handler_subclass():
     assert c.get('/child-registered').data == b'child-registered'
 
 
-def test_error_handler_http_subclass():
-    app = flask.Flask(__name__)
-
+def test_error_handler_http_subclass(app):
     class ForbiddenSubclassRegistered(Forbidden):
         pass
 
@@ -116,7 +110,7 @@ def test_error_handler_http_subclass():
     assert c.get('/forbidden-registered').data == b'forbidden-registered'
 
 
-def test_error_handler_blueprint():
+def test_error_handler_blueprint(app):
     bp = flask.Blueprint('bp', __name__)
 
     @bp.errorhandler(500)
@@ -127,8 +121,6 @@ def test_error_handler_blueprint():
     def bp_test():
         raise InternalServerError()
 
-    app = flask.Flask(__name__)
-
     @app.errorhandler(500)
     def app_exception_handler(e):
         return 'app-error'