diff --git a/appveyor.yml b/appveyor.yml
index 79c6e6dddc..96226fca99 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -21,7 +21,7 @@ environment:
 platform:
   - x64
 
-build: off
+build: false
 
 install:
   - cmd: call %CONDA_INSTALL_LOCN%\Scripts\activate.bat
@@ -31,11 +31,11 @@ install:
   - cmd: conda config --add channels conda-forge
   - cmd: conda update --yes --quiet conda
   - cmd: conda info -a
-  - cmd: conda create -y -q -n test-env-%CONDA_PY% python=%CONDA_PY_SPEC% pyzmq tornado jupyter_client nbformat nbconvert ipykernel pip nose
+  - cmd: conda create -y -q -n test-env-%CONDA_PY% python=%CONDA_PY_SPEC% pip pyzmq tornado jupyter_client nbformat nbconvert nose
   - cmd: conda activate test-env-%CONDA_PY%
-  - cmd: pip install .[test]
+  - cmd: pip install -e .[test]
 # FIXME: Use patch for python 3.8, windows issues (https://github.com/ipython/ipykernel/pull/456) - remove once released
   - IF %CONDA_PY% == 38 pip install --upgrade git+https://github.com/ipython/ipykernel.git
 
 test_script:
-  - pytest
+  - pytest -s -v
diff --git a/jupyter_server/pytest_plugin.py b/jupyter_server/pytest_plugin.py
new file mode 100644
index 0000000000..a889c23a45
--- /dev/null
+++ b/jupyter_server/pytest_plugin.py
@@ -0,0 +1,216 @@
+import os
+import sys
+import json
+import pytest
+import asyncio
+from binascii import hexlify
+
+import urllib.parse
+import tornado
+from tornado.escape import url_escape
+
+from traitlets.config import Config
+
+import jupyter_core.paths
+from jupyter_server.extension import serverextension
+from jupyter_server.serverapp import ServerApp
+from jupyter_server.utils import url_path_join
+
+import nbformat
+
+# This shouldn't be needed anymore, since pytest_tornasync is found in entrypoints
+pytest_plugins = "pytest_tornasync"
+
+# NOTE: This is a temporary fix for Windows 3.8
+# We have to override the io_loop fixture with an
+# asyncio patch. This will probably be removed in
+# the future.
+
+@pytest.fixture
+def asyncio_patch():
+    ServerApp()._init_asyncio_patch()
+
+@pytest.fixture
+def io_loop(asyncio_patch):
+    loop = tornado.ioloop.IOLoop()
+    loop.make_current()
+    yield loop
+    loop.clear_current()
+    loop.close(all_fds=True)
+
+
+def mkdir(tmp_path, *parts):
+    path = tmp_path.joinpath(*parts)
+    if not path.exists():
+        path.mkdir(parents=True)
+    return path
+
+
+config = pytest.fixture(lambda: {})
+home_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, "home"))
+data_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, "data"))
+config_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, "config"))
+runtime_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, "runtime"))
+root_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, "root_dir"))
+system_jupyter_path = pytest.fixture(
+    lambda tmp_path: mkdir(tmp_path, "share", "jupyter")
+)
+env_jupyter_path = pytest.fixture(
+    lambda tmp_path: mkdir(tmp_path, "env", "share", "jupyter")
+)
+system_config_path = pytest.fixture(lambda tmp_path: mkdir(tmp_path, "etc", "jupyter"))
+env_config_path = pytest.fixture(
+    lambda tmp_path: mkdir(tmp_path, "env", "etc", "jupyter")
+)
+argv = pytest.fixture(lambda: [])
+
+
+@pytest.fixture
+def environ(
+    monkeypatch,
+    tmp_path,
+    home_dir,
+    data_dir,
+    config_dir,
+    runtime_dir,
+    root_dir,
+    system_jupyter_path,
+    system_config_path,
+    env_jupyter_path,
+    env_config_path,
+):
+    monkeypatch.setenv("HOME", str(home_dir))
+    monkeypatch.setenv("PYTHONPATH", os.pathsep.join(sys.path))
+    monkeypatch.setenv("JUPYTER_NO_CONFIG", "1")
+    monkeypatch.setenv("JUPYTER_CONFIG_DIR", str(config_dir))
+    monkeypatch.setenv("JUPYTER_DATA_DIR", str(data_dir))
+    monkeypatch.setenv("JUPYTER_RUNTIME_DIR", str(runtime_dir))
+    monkeypatch.setattr(
+        jupyter_core.paths, "SYSTEM_JUPYTER_PATH", [str(system_jupyter_path)]
+    )
+    monkeypatch.setattr(jupyter_core.paths, "ENV_JUPYTER_PATH", [str(env_jupyter_path)])
+    monkeypatch.setattr(
+        jupyter_core.paths, "SYSTEM_CONFIG_PATH", [str(system_config_path)]
+    )
+    monkeypatch.setattr(jupyter_core.paths, "ENV_CONFIG_PATH", [str(env_config_path)])
+
+
+@pytest.fixture
+def extension_environ(env_config_path, monkeypatch):
+    """Monkeypatch a Jupyter Extension's config path into each test's environment variable"""
+    monkeypatch.setattr(serverextension, "ENV_CONFIG_PATH", [str(env_config_path)])
+    monkeypatch.setattr(serverextension, "ENV_CONFIG_PATH", [str(env_config_path)])
+
+
+@pytest.fixture
+def configurable_serverapp(
+    environ, http_port, tmp_path, home_dir, data_dir, config_dir, runtime_dir, root_dir, io_loop
+):
+    def serverapp(
+        config={},
+        argv=[],
+        environ=environ,
+        http_port=http_port,
+        tmp_path=tmp_path,
+        home_dir=home_dir,
+        data_dir=data_dir,
+        config_dir=config_dir,
+        runtime_dir=runtime_dir,
+        root_dir=root_dir,
+        **kwargs
+    ):
+        c = Config(config)
+        c.NotebookNotary.db_file = ":memory:"
+        token = hexlify(os.urandom(4)).decode("ascii")
+        url_prefix = "/"
+        app = ServerApp.instance(
+            port=http_port,
+            port_retries=0,
+            open_browser=False,
+            config_dir=str(config_dir),
+            data_dir=str(data_dir),
+            runtime_dir=str(runtime_dir),
+            root_dir=str(root_dir),
+            base_url=url_prefix,
+            config=c,
+            allow_root=True,
+            token=token,
+            **kwargs
+        )
+        app.init_signal = lambda: None
+        app.log.propagate = True
+        app.log.handlers = []
+        # Initialize app without httpserver
+        app.initialize(argv=argv, new_httpserver=False)
+        app.log.propagate = True
+        app.log.handlers = []
+        # Start app without ioloop
+        app.start_app()
+        return app
+
+    yield serverapp
+    ServerApp.clear_instance()
+
+
+@pytest.fixture
+def serverapp(configurable_serverapp, config, argv):
+    app = configurable_serverapp(config=config, argv=argv)
+    yield app
+    app.remove_server_info_file()
+    app.remove_browser_open_file()
+    app.cleanup_kernels()
+
+
+@pytest.fixture
+def app(serverapp):
+    return serverapp.web_app
+
+
+@pytest.fixture
+def auth_header(serverapp):
+    return {"Authorization": "token {token}".format(token=serverapp.token)}
+
+
+@pytest.fixture
+def http_port(http_server_port):
+    return http_server_port[-1]
+
+
+@pytest.fixture
+def base_url(http_server_port):
+    return "/"
+
+
+@pytest.fixture
+def fetch(http_server_client, auth_header, base_url):
+    """fetch fixture that handles auth, base_url, and path"""
+    def client_fetch(*parts, headers={}, params={}, **kwargs):
+        # Handle URL strings
+        path_url = url_escape(url_path_join(base_url, *parts), plus=False)
+        params_url = urllib.parse.urlencode(params)
+        url = path_url + "?" + params_url
+        # Add auth keys to header
+        headers.update(auth_header)
+        # Make request.
+        return http_server_client.fetch(
+            url, headers=headers, request_timeout=20, **kwargs
+        )
+    return client_fetch
+
+
+@pytest.fixture
+def create_notebook(root_dir):
+    """Create a notebook in the test's home directory."""
+    def inner(nbpath):
+        nbpath = root_dir.joinpath(nbpath)
+        # Check that the notebook has the correct file extension.
+        if nbpath.suffix != '.ipynb':
+            raise Exception("File extension for notebook must be .ipynb")
+        # If the notebook path has a parent directory, make sure it's created.
+        parent = nbpath.parent
+        parent.mkdir(parents=True, exist_ok=True)
+        # Create a notebook string and write to file.
+        nb = nbformat.v4.new_notebook()
+        nbtext = nbformat.writes(nb, version=4)
+        nbpath.write_text(nbtext)
+    return inner
diff --git a/setup.py b/setup.py
index 1e5d636f9f..a30ce3a886 100755
--- a/setup.py
+++ b/setup.py
@@ -100,6 +100,9 @@
         'console_scripts': [
             'jupyter-server = jupyter_server.serverapp:main',
             'jupyter-bundlerextension = jupyter_server.bundler.bundlerextensions:main',
+        ],
+        'pytest11': [
+            'pytest_jupyter_server = jupyter_server.pytest_plugin'
         ]
     },
 )
diff --git a/tests/conftest.py b/tests/conftest.py
index 225fc8907b..9d694425b2 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,207 +1 @@
-import os
-import sys
-import json
-import pytest
-import asyncio
-from binascii import hexlify
-
-import urllib.parse
-import tornado
-from tornado.escape import url_escape
-
-from traitlets.config import Config
-
-import jupyter_core.paths
-import jupyter_server.extension.serverextension
-from jupyter_server.serverapp import ServerApp
-from jupyter_server.utils import url_path_join
-
-
-pytest_plugins = ("pytest_tornasync")
-
-
-# NOTE: This is a temporary fix for Windows 3.8
-# We have to override the io_loop fixture with an 
-# asyncio patch. This will probably be removed in 
-# the future.                   
-if sys.platform.startswith("win") and sys.version_info >= (3, 8):
-
-    @pytest.fixture
-    def asyncio_patch():
-        ServerApp()._init_asyncio_patch()
-
-    @pytest.fixture
-    def io_loop(asyncio_patch):
-        loop = tornado.ioloop.IOLoop()
-        loop.make_current()
-        yield loop
-        loop.clear_current()
-        loop.close(all_fds=True)
-
-
-def mkdir(tmp_path, *parts):
-    path = tmp_path.joinpath(*parts)
-    if not path.exists():
-        path.mkdir(parents=True)
-    return path
-
-
-def expected_http_error(error, expected_code, expected_message=None):
-    """Check that the error matches the expected output error."""
-    e = error.value
-    if isinstance(e, tornado.web.HTTPError):
-        if expected_code != e.status_code:
-            return False
-        if expected_message is not None and expected_message != str(e):
-            return False
-        return True
-    elif any([
-        isinstance(e, tornado.httpclient.HTTPClientError), 
-        isinstance(e, tornado.httpclient.HTTPError)
-    ]):
-        if expected_code != e.code:
-            return False
-        if expected_message:
-            message = json.loads(e.response.body.decode())['message']
-            if expected_message != message:
-                return False
-        return True
-
-
-config = pytest.fixture(lambda: {})
-home_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, 'home'))
-data_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, 'data'))
-config_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, 'config'))
-runtime_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, 'runtime'))
-root_dir = pytest.fixture(lambda tmp_path: mkdir(tmp_path, 'root_dir'))
-system_jupyter_path = pytest.fixture(lambda tmp_path: mkdir(tmp_path, 'share', 'jupyter'))
-env_jupyter_path = pytest.fixture(lambda tmp_path: mkdir(tmp_path, 'env', 'share', 'jupyter'))
-system_config_path = pytest.fixture(lambda tmp_path: mkdir(tmp_path, 'etc', 'jupyter'))
-env_config_path = pytest.fixture(lambda tmp_path: mkdir(tmp_path, 'env', 'etc', 'jupyter'))
-argv = pytest.fixture(lambda: [])
-
-@pytest.fixture
-def environ(
-    monkeypatch,
-    tmp_path,
-    home_dir,
-    data_dir,
-    config_dir,
-    runtime_dir,
-    root_dir,
-    system_jupyter_path,
-    system_config_path,
-    env_jupyter_path,
-    env_config_path
-    ):
-    monkeypatch.setenv('HOME', str(home_dir))
-    monkeypatch.setenv('PYTHONPATH', os.pathsep.join(sys.path))
-    monkeypatch.setenv('JUPYTER_NO_CONFIG', '1')
-    monkeypatch.setenv('JUPYTER_CONFIG_DIR', str(config_dir))
-    monkeypatch.setenv('JUPYTER_DATA_DIR', str(data_dir))
-    monkeypatch.setenv('JUPYTER_RUNTIME_DIR', str(runtime_dir))
-    monkeypatch.setattr(jupyter_core.paths, 'SYSTEM_JUPYTER_PATH', [str(system_jupyter_path)])
-    monkeypatch.setattr(jupyter_core.paths, 'ENV_JUPYTER_PATH', [str(env_jupyter_path)])
-    monkeypatch.setattr(jupyter_core.paths, 'SYSTEM_CONFIG_PATH', [str(system_config_path)])
-    monkeypatch.setattr(jupyter_core.paths, 'ENV_CONFIG_PATH', [str(env_config_path)])
-
-
-@pytest.fixture
-def configurable_serverapp(    
-    environ,
-    http_port, 
-    tmp_path, 
-    home_dir,
-    data_dir,
-    config_dir,
-    runtime_dir,
-    root_dir
-    ):
-
-    def serverapp(
-        config={}, 
-        argv=[], 
-        environ=environ,
-        http_port=http_port, 
-        tmp_path=tmp_path, 
-        home_dir=home_dir,
-        data_dir=data_dir,
-        config_dir=config_dir,
-        runtime_dir=runtime_dir,
-        root_dir=root_dir,
-        **kwargs):
-        c = Config(config)
-        c.NotebookNotary.db_file = ':memory:'
-        token = hexlify(os.urandom(4)).decode('ascii')
-        url_prefix = '/'
-        app = ServerApp.instance(
-            port=http_port,
-            port_retries=0,
-            open_browser=False,
-            config_dir=str(config_dir),
-            data_dir=str(data_dir),
-            runtime_dir=str(runtime_dir),
-            root_dir=str(root_dir),
-            base_url=url_prefix,
-            config=c,
-            allow_root=True,
-            token=token,
-            **kwargs
-        )
-        app.init_signal = lambda : None
-        app.log.propagate = True
-        app.log.handlers = []
-        # Initialize app without httpserver
-        app.initialize(argv=argv, new_httpserver=False)
-        app.log.propagate = True
-        app.log.handlers = []
-        # Start app without ioloop
-        app.start_app()
-        return app
-
-    yield serverapp
-    ServerApp.clear_instance()
-
-
-@pytest.fixture
-def serverapp(configurable_serverapp, config, argv):
-    app = configurable_serverapp(config=config, argv=argv)
-    yield app
-    app.remove_server_info_file()
-    app.remove_browser_open_file()
-    app.cleanup_kernels()
-
-
-@pytest.fixture
-def app(serverapp):
-    return serverapp.web_app
-
-
-@pytest.fixture
-def auth_header(serverapp):
-    return {'Authorization': 'token {token}'.format(token=serverapp.token)}
-
-
-@pytest.fixture
-def http_port(http_server_port):
-    return http_server_port[-1]
-
-
-@pytest.fixture
-def base_url(http_server_port):
-    return '/'
-
-
-@pytest.fixture
-def fetch(http_server_client, auth_header, base_url):
-    """fetch fixture that handles auth, base_url, and path"""
-    def client_fetch(*parts, headers={}, params={}, **kwargs):
-        # Handle URL strings
-        path_url = url_escape(url_path_join(base_url, *parts), plus=False)
-        params_url = urllib.parse.urlencode(params)
-        url = path_url + "?" + params_url
-        # Add auth keys to header
-        headers.update(auth_header)
-        # Make request.
-        return http_server_client.fetch(url, headers=headers, request_timeout=20, **kwargs)
-    return client_fetch
\ No newline at end of file
+pytest_plugins = ['pytest_jupyter_server']
\ No newline at end of file
diff --git a/tests/extension/conftest.py b/tests/extension/conftest.py
index 1dbf2170d2..8505ac0220 100644
--- a/tests/extension/conftest.py
+++ b/tests/extension/conftest.py
@@ -34,21 +34,17 @@ def _jupyter_server_extension_paths():
         }]
 
 
-@pytest.fixture
-def extension_environ(env_config_path, monkeypatch):
-    monkeypatch.setattr(serverextension, 'ENV_CONFIG_PATH', [str(env_config_path)])
-    monkeypatch.setattr(serverextension, 'ENV_CONFIG_PATH', [str(env_config_path)])
-
-
 @pytest.fixture
 def config_file(config_dir):
-    f = config_dir.joinpath('jupyter_mockextension_config.py')
+    """"""
+    f = config_dir.joinpath("jupyter_mockextension_config.py")
     f.write_text("c.MockExtensionApp.mock_trait ='config from file'")
     return f
 
 
 @pytest.fixture
 def extended_serverapp(serverapp):
+    """"""
     m = MockExtensionApp()
     m.initialize(serverapp)
     return m
@@ -56,7 +52,12 @@ def extended_serverapp(serverapp):
 
 @pytest.fixture
 def inject_mock_extension(environ, extension_environ):
-    def ext(modulename='mockextension'):
+    """Fixture that can be used to inject a mock Jupyter Server extension into the tests namespace.
+
+        Usage: inject_mock_extension({'extension_name': ExtensionClass})
+    """
+    def ext(modulename="mockextension"):
         sys.modules[modulename] = e = MockExtensionApp()
         return e
+
     return ext
diff --git a/tests/extension/test_entrypoint.py b/tests/extension/test_entrypoint.py
index e07bb00c4f..f79fe5471d 100644
--- a/tests/extension/test_entrypoint.py
+++ b/tests/extension/test_entrypoint.py
@@ -3,6 +3,8 @@
 from jupyter_core import paths
 from jupyter_server.extension import serverextension
 
+from .conftest import MockExtensionApp
+
 # All test coroutines will be treated as marked.
 pytestmark = pytest.mark.script_launch_mode('subprocess')
 
@@ -15,9 +17,10 @@ def test_server_extension_list(environ, script_runner):
 def test_server_extension_enable(environ, inject_mock_extension, script_runner):
     # 'mock' is not a valid extension The entry point should complete
     # but print to sterr.
+    extension_name = "mockextension"
     inject_mock_extension()
-    extension_name = 'mockextension'
-    ret = script_runner.run('jupyter', 'server', 'extension', 'enable', extension_name)
+
+    ret = script_runner.run("jupyter", "server", "extension", "enable", extension_name)
     assert ret.success
     assert 'Enabling: {}'.format(extension_name) in ret.stderr
 
diff --git a/tests/extension/test_serverextension.py b/tests/extension/test_serverextension.py
index 3c71eb694f..3ff969d82c 100644
--- a/tests/extension/test_serverextension.py
+++ b/tests/extension/test_serverextension.py
@@ -6,13 +6,13 @@
 
 from traitlets.tests.utils import check_help_all_output
 
-from ..conftest import mkdir
+from ..utils import mkdir
 
 from jupyter_server.serverapp import ServerApp
 from jupyter_server.extension import serverextension
 from jupyter_server.extension.serverextension import (
     validate_server_extension,
-    toggle_server_extension_python, 
+    toggle_server_extension_python,
     _get_config_dir
 )
 from jupyter_server.config_manager import BaseJSONConfigManager
@@ -49,8 +49,8 @@ def test_disable(inject_mock_extension):
 
 
 def test_merge_config(
-    env_config_path, 
-    inject_mock_extension, 
+    env_config_path,
+    inject_mock_extension,
     configurable_serverapp
     ):
     # enabled at sys level
@@ -79,7 +79,7 @@ def test_merge_config(
 
     # Enable the last extension, mockext_py, using the CLI interface.
     app = configurable_serverapp(
-        config_dir=str(env_config_path), 
+        config_dir=str(env_config_path),
         argv=['--ServerApp.jpserver_extensions={"mockext_py":True}']
     )
     # Verify that extensions are enabled and merged properly.
diff --git a/tests/nbconvert/test_handlers.py b/tests/nbconvert/test_handlers.py
index 12a7256d26..b5ec68c681 100644
--- a/tests/nbconvert/test_handlers.py
+++ b/tests/nbconvert/test_handlers.py
@@ -18,7 +18,7 @@
 
 import pytest
 
-from ..conftest import expected_http_error
+from ..utils import expected_http_error
 
 
 png_green_pixel = encodebytes(b'\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00'
diff --git a/tests/services/contents/test_api.py b/tests/services/contents/test_api.py
index 7dbd3fd759..d99069b9c5 100644
--- a/tests/services/contents/test_api.py
+++ b/tests/services/contents/test_api.py
@@ -15,7 +15,7 @@
 
 from base64 import encodebytes, decodebytes
 
-from ...conftest import expected_http_error
+from ...utils import expected_http_error
 
 
 def notebooks_only(dir_model):
@@ -118,7 +118,7 @@ async def test_get_nb_contents(fetch, contents, path, name):
     r = await fetch(
         'api', 'contents', nbpath,
         method='GET',
-        params=dict(content='1') 
+        params=dict(content='1')
     )
     model = json.loads(r.body.decode())
     assert model['name'] == nbname
@@ -137,7 +137,7 @@ async def test_get_nb_no_contents(fetch, contents, path, name):
     r = await fetch(
         'api', 'contents', nbpath,
         method='GET',
-        params=dict(content='0') 
+        params=dict(content='0')
     )
     model = json.loads(r.body.decode())
     assert model['name'] == nbname
@@ -186,7 +186,7 @@ async def test_get_text_file_contents(fetch, contents, path, name):
     r = await fetch(
         'api', 'contents', txtpath,
         method='GET',
-        params=dict(content='1') 
+        params=dict(content='1')
     )
     model = json.loads(r.body.decode())
     assert model['name'] == txtname
@@ -223,7 +223,7 @@ async def test_get_binary_file_contents(fetch, contents, path, name):
     r = await fetch(
         'api', 'contents', blobpath,
         method='GET',
-        params=dict(content='1') 
+        params=dict(content='1')
     )
     model = json.loads(r.body.decode())
     assert model['name'] == blobname
@@ -285,7 +285,7 @@ async def test_create_untitled(fetch, contents, contents_dir):
     path = 'å b'
     name = 'Untitled.ipynb'
     r = await fetch(
-        'api', 'contents', path, 
+        'api', 'contents', path,
         method='POST',
         body=json.dumps({'ext': '.ipynb'})
     )
@@ -293,7 +293,7 @@ async def test_create_untitled(fetch, contents, contents_dir):
 
     name = 'Untitled1.ipynb'
     r = await fetch(
-        'api', 'contents', path, 
+        'api', 'contents', path,
         method='POST',
         body=json.dumps({'ext': '.ipynb'})
     )
@@ -302,7 +302,7 @@ async def test_create_untitled(fetch, contents, contents_dir):
     path = 'foo/bar'
     name = 'Untitled.ipynb'
     r = await fetch(
-        'api', 'contents', path, 
+        'api', 'contents', path,
         method='POST',
         body=json.dumps({'ext': '.ipynb'})
     )
@@ -313,7 +313,7 @@ async def test_create_untitled_txt(fetch, contents, contents_dir):
     name = 'untitled.txt'
     path = 'foo/bar'
     r = await fetch(
-        'api', 'contents', path, 
+        'api', 'contents', path,
         method='POST',
         body=json.dumps({'ext': '.txt'})
     )
@@ -456,7 +456,7 @@ async def test_copy(fetch, contents, contents_dir):
         body=json.dumps({'copy_from': path+'/'+name})
     )
     _check_created(r, str(contents_dir), path, copy, type='notebook')
-    
+
     # Copy the same file name
     copy2 = 'ç d-Copy2.ipynb'
     r = await fetch(
@@ -601,14 +601,14 @@ async def test_rename(fetch, contents, contents_dir):
 async def test_checkpoints_follow_file(fetch, contents):
     path = 'foo'
     name = 'a.ipynb'
-    
+
     # Read initial file.
     r = await fetch(
         'api', 'contents', path, name,
         method='GET'
     )
     model = json.loads(r.body.decode())
-    
+
     # Create a checkpoint of initial state
     r = await fetch(
         'api', 'contents', path, name, 'checkpoints',
@@ -616,7 +616,7 @@ async def test_checkpoints_follow_file(fetch, contents):
         allow_nonstandard_methods=True
     )
     cp1 = json.loads(r.body.decode())
-    
+
     # Modify file and save.
     nbcontent = model['content']
     nb = from_dict(nbcontent)
@@ -690,7 +690,7 @@ async def test_checkpoints(fetch, contents):
     path = 'foo/a.ipynb'
     resp = await fetch(
         'api', 'contents', path,
-        method='GET' 
+        method='GET'
     )
     model = json.loads(resp.body.decode())
     r = await fetch(
@@ -708,7 +708,7 @@ async def test_checkpoints(fetch, contents):
     nb = from_dict(nbcontent)
     hcell = new_markdown_cell('Created by test')
     nb.cells.append(hcell)
-    
+
     # Save it.
     nbmodel = {'content': nb, 'type': 'notebook'}
     resp = await fetch(
@@ -716,7 +716,7 @@ async def test_checkpoints(fetch, contents):
         method='PUT',
         body=json.dumps(nbmodel)
     )
-    
+
     # List checkpoints
     r = await fetch(
         'api', 'contents', path, 'checkpoints',
@@ -727,7 +727,7 @@ async def test_checkpoints(fetch, contents):
 
     r = await fetch(
         'api', 'contents', path,
-        method='GET' 
+        method='GET'
     )
     nbcontent = json.loads(r.body.decode())['content']
     nb = from_dict(nbcontent)
@@ -768,7 +768,7 @@ async def test_file_checkpoints(fetch, contents):
     path = 'foo/a.txt'
     resp = await fetch(
         'api', 'contents', path,
-        method='GET' 
+        method='GET'
     )
     orig_content = json.loads(resp.body.decode())['content']
     r = await fetch(
@@ -788,14 +788,14 @@ async def test_file_checkpoints(fetch, contents):
         'type': 'file',
         'format': 'text',
     }
-    
+
     # Save it.
     resp = await fetch(
         'api', 'contents', path,
         method='PUT',
         body=json.dumps(model)
     )
-    
+
     # List checkpoints
     r = await fetch(
         'api', 'contents', path, 'checkpoints',
@@ -806,7 +806,7 @@ async def test_file_checkpoints(fetch, contents):
 
     r = await fetch(
         'api', 'contents', path,
-        method='GET' 
+        method='GET'
     )
     content = json.loads(r.body.decode())['content']
     assert content == new_content
diff --git a/tests/services/contents/test_largefilemanager.py b/tests/services/contents/test_largefilemanager.py
index bf4e3d24c9..fcacaf2729 100644
--- a/tests/services/contents/test_largefilemanager.py
+++ b/tests/services/contents/test_largefilemanager.py
@@ -2,7 +2,7 @@
 import tornado
 
 from jupyter_server.services.contents.largefilemanager import LargeFileManager
-from ...conftest import expected_http_error
+from ...utils import expected_http_error
 
 contents_manager = pytest.fixture(lambda tmp_path: LargeFileManager(root_dir=str(tmp_path)))
 
@@ -28,7 +28,7 @@ def test_save(contents_manager):
     'model,err_message',
     [
         (
-            {'name': 'test', 'path': 'test', 'chunk': 1}, 
+            {'name': 'test', 'path': 'test', 'chunk': 1},
             'HTTP 400: Bad Request (No file type provided)'
         ),
         (
@@ -40,7 +40,7 @@ def test_save(contents_manager):
             'HTTP 400: Bad Request (No file content provided)',
         ),
         (
-            {'name': 'test', 'path': 'test', 'chunk': 2, 'type': 'file', 
+            {'name': 'test', 'path': 'test', 'chunk': 2, 'type': 'file',
                 'content': u'test', 'format': 'json'},
             "HTTP 400: Bad Request (Must specify format of file contents as 'text' or 'base64')"
         )
diff --git a/tests/services/contents/test_manager.py b/tests/services/contents/test_manager.py
index 526e53050e..ef6f29d6cf 100644
--- a/tests/services/contents/test_manager.py
+++ b/tests/services/contents/test_manager.py
@@ -11,7 +11,7 @@
 from nbformat import v4 as nbformat
 
 from jupyter_server.services.contents.filemanager import FileContentsManager
-from ...conftest import expected_http_error
+from ...utils import expected_http_error
 
 # -------------- Functions ----------------------------
 
@@ -141,7 +141,7 @@ def test_checkpoint_subdir(tmp_path):
 
 
 @pytest.mark.skipif(
-    sys.platform == 'win32' and sys.version_info[0] < 3, 
+    sys.platform == 'win32' and sys.version_info[0] < 3,
     reason="System platform is Windows, version < 3"
 )
 def test_bad_symlink(tmp_path):
@@ -166,7 +166,7 @@ def test_bad_symlink(tmp_path):
 
 
 @pytest.mark.skipif(
-    sys.platform == 'win32' and sys.version_info[0] < 3, 
+    sys.platform == 'win32' and sys.version_info[0] < 3,
     reason="System platform is Windows, version < 3"
 )
 def test_good_symlink(tmp_path):
@@ -354,7 +354,7 @@ def test_get(contents_manager):
     for key, value in expected_model.items():
         assert file_model[key] == value
     assert 'created' in file_model
-    assert 'last_modified' in file_model 
+    assert 'last_modified' in file_model
 
     # Create a sub-sub directory to test getting directory contents with a
     # subdir.
@@ -516,7 +516,7 @@ def test_rename(contents_manager):
     # Creating a notebook in a non_existant directory should fail
     with pytest.raises(HTTPError) as e:
         cm.new_untitled("foo/bar_diff", ext=".ipynb")
-    assert expected_http_error(e, 404)        
+    assert expected_http_error(e, 404)
 
     cm.rename("foo/bar", "foo/bar_diff")
 
diff --git a/tests/services/kernels/test_api.py b/tests/services/kernels/test_api.py
index cfdc6b80c1..7c1a123033 100644
--- a/tests/services/kernels/test_api.py
+++ b/tests/services/kernels/test_api.py
@@ -10,7 +10,7 @@
 from jupyter_client.kernelspec import NATIVE_KERNEL_NAME
 
 from jupyter_server.utils import url_path_join
-from ...conftest import expected_http_error
+from ...utils import expected_http_error
 
 
 @pytest.fixture
@@ -29,7 +29,7 @@ def client_fetch(*parts, headers={}, params={}, **kwargs):
         headers.update(auth_header)
         # Make request.
         req = tornado.httpclient.HTTPRequest(
-            url, 
+            url,
             headers=auth_header,
             connect_timeout=120
         )
@@ -204,7 +204,7 @@ async def test_connection(fetch, ws_fetch, http_port, auth_header):
         })
     )
     kid = json.loads(r.body.decode())['id']
-    
+
     # Get kernel info
     r = await fetch(
         'api', 'kernels', kid,
@@ -218,7 +218,7 @@ async def test_connection(fetch, ws_fetch, http_port, auth_header):
     ws = await ws_fetch(
         'api', 'kernels', kid, 'channels'
     )
-    
+
     # Test that it was opened.
     r = await fetch(
         'api', 'kernels', kid,
@@ -240,7 +240,7 @@ async def test_connection(fetch, ws_fetch, http_port, auth_header):
             time.sleep(0.1)
         else:
             break
-    
+
     r = await fetch(
         'api', 'kernels', kid,
         method='GET'
diff --git a/tests/services/kernelspecs/test_api.py b/tests/services/kernelspecs/test_api.py
index 0d3a2ba387..3768a64d45 100644
--- a/tests/services/kernelspecs/test_api.py
+++ b/tests/services/kernelspecs/test_api.py
@@ -5,7 +5,7 @@
 
 from jupyter_client.kernelspec import NATIVE_KERNEL_NAME
 
-from ...conftest import expected_http_error
+from ...utils import expected_http_error
 
 
 sample_kernel_json = {
diff --git a/tests/services/sessions/test_api.py b/tests/services/sessions/test_api.py
index 31b9ef5d87..2d9bca0124 100644
--- a/tests/services/sessions/test_api.py
+++ b/tests/services/sessions/test_api.py
@@ -8,7 +8,7 @@
 from nbformat.v4 import new_notebook
 from nbformat import writes
 
-from ...conftest import expected_http_error
+from ...utils import expected_http_error
 
 j = lambda r: json.loads(r.body.decode())
 
@@ -37,9 +37,9 @@ async def get(self, id):
         return await self._req(id, method='GET')
 
     async def create(
-        self, 
-        path, 
-        type='notebook', 
+        self,
+        path,
+        type='notebook',
         kernel_name='python',
         kernel_id=None):
         body = {
@@ -114,7 +114,7 @@ def session_client(root_dir, fetch):
 
     # Remove subdir
     shutil.rmtree(str(subdir), ignore_errors=True)
-    
+
 
 async def test_create(session_client):
     # Make sure no sessions exist.
@@ -170,7 +170,7 @@ async def test_create_deprecated(session_client):
     assert resp.code == 201
     newsession = j(resp)
     assert newsession['path'] == 'foo/nb1.ipynb'
-    assert newsession['type'] == 'notebook' 
+    assert newsession['type'] == 'notebook'
     assert newsession['notebook']['path'] == 'foo/nb1.ipynb'
     # Need to find a better solution to this.
     await session_client.cleanup()
diff --git a/tests/test_files.py b/tests/test_files.py
index 0185c0e2fa..e65dc2da93 100644
--- a/tests/test_files.py
+++ b/tests/test_files.py
@@ -2,7 +2,7 @@
 import pytest
 import tornado
 
-from .conftest import expected_http_error
+from .utils import expected_http_error
 
 from nbformat import writes
 from nbformat.v4 import (new_notebook,
@@ -112,7 +112,7 @@ async def test_contents_manager(fetch, serverapp, root_dir):
     assert r.headers['content-type'] == 'application/octet-stream'
     assert r.body[:1] == b'\xff'
     assert len(r.body) == 6
- 
+
     r = await fetch(
         'files/test.txt',
         method='GET'
diff --git a/tests/test_gateway.py b/tests/test_gateway.py
index 4ad4d71a68..9084f15fb4 100644
--- a/tests/test_gateway.py
+++ b/tests/test_gateway.py
@@ -14,7 +14,7 @@
 
 from unittest.mock import patch
 from io import StringIO
-from .conftest import expected_http_error
+from .utils import expected_http_error
 
 
 def generate_kernelspec(name):
diff --git a/tests/utils.py b/tests/utils.py
new file mode 100644
index 0000000000..819d62aa5e
--- /dev/null
+++ b/tests/utils.py
@@ -0,0 +1,31 @@
+import json
+import tornado
+
+
+def mkdir(tmp_path, *parts):
+    path = tmp_path.joinpath(*parts)
+    if not path.exists():
+        path.mkdir(parents=True)
+    return path
+
+
+def expected_http_error(error, expected_code, expected_message=None):
+    """Check that the error matches the expected output error."""
+    e = error.value
+    if isinstance(e, tornado.web.HTTPError):
+        if expected_code != e.status_code:
+            return False
+        if expected_message is not None and expected_message != str(e):
+            return False
+        return True
+    elif any([
+        isinstance(e, tornado.httpclient.HTTPClientError),
+        isinstance(e, tornado.httpclient.HTTPError)
+    ]):
+        if expected_code != e.code:
+            return False
+        if expected_message:
+            message = json.loads(e.response.body.decode())['message']
+            if expected_message != message:
+                return False
+        return True