diff --git a/.gitignore b/.gitignore
index 083d732..5b5b88a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 __pycache__
 .idea
+tests/api_key
diff --git a/README.rst b/README.rst
index 257b115..61fb864 100644
--- a/README.rst
+++ b/README.rst
@@ -9,17 +9,18 @@ The tests are run regularly on travis-ci.com.
 
 Running the tests
 -----------------
-You need to have Python 3 installed. Either define the environment variable
+You need to have Python 3 installed. You may define the environment variable
 `DCOR_API_KEY` or create the file `api_key` containing your API key in the
-`tests` directory. Then run:
+`tests` directory. Otherwise, a test user is created automatically on DCOR-dev
+and its API key is stored in `tests/api_key`. Then run:
 
 ::
 
     pip install -r requirements
     py.test tests
 
-Note that datasets, collections, and circles created during testing are
-only purged for registered testing users (e.g. "remote_tester").
+Note that all users, datasets, collections, and circles on DCOR-dev are
+purged regularly.
 
 
 .. |Tests Status| image:: https://img.shields.io/github/actions/workflow/status/DCOR-dev/dcor-remote-tests/check.yml
diff --git a/tests/helper.py b/tests/helper.py
index 5b40a0a..26393b7 100644
--- a/tests/helper.py
+++ b/tests/helper.py
@@ -1,9 +1,10 @@
+import functools
 import inspect
 import os
 import pathlib
 import time
 
-from dcoraid.api import CKANAPI
+from dcoraid.api import CKANAPI, create_dcor_dev_user, is_valid_api_key
 
 
 SERVER = "dcor-dev.mpl.mpg.de"
@@ -14,24 +15,43 @@ def get_api():
     return api
 
 
+@functools.lru_cache
 def get_api_key():
+    """Return the API key of the test user
+
+    The API key is taken from the `DCOR_API_KEY` environment variable.
+    If that is not set, the key stored in the file `tests/api_key` is
+    used. If that file does not exist or the key is invalid (users on
+    DCOR-dev are purged regularly), a new user is created on DCOR-dev
+    and its API key is written to `tests/api_key`.
+    """
     key = os.environ.get("DCOR_API_KEY")
     if not key:
-        # local file
         kp = pathlib.Path(__file__).parent / "api_key"
-        if not kp.exists():
-            raise ValueError("No DCOR_API_KEY variable or api_key file!")
-        key = kp.read_text().strip()
+        if kp.exists():
+            key = kp.read_text().strip()
+        if not is_valid_api_key(server=SERVER, api_key=key):
+            key = create_dcor_dev_user(server=SERVER,
+                                       fullname="DCOR remote tester")
+            kp.write_text(key)
     return key
 
 
+@functools.lru_cache
+def get_user_name():
+    """Return the name of the test user"""
+    return get_api().get_user_dict()["name"]
+
+
 def make_dataset_dict(circle=None, hint=None):
     """Generate a test dataset in a test circle
 
     Parameters
     ----------
     circle: str or None
-        circle name; if None, the calling functions module is used
+        circle name; if None, the calling functions module is used,
+        prefixed with the name of the test user (circle names are
+        unique on DCOR and test users are created on the fly)
     hint: str
         descriptive dataset title string; if None, the calling function
         is used; the time since the epoch is added to the dataset title
@@ -41,7 +61,8 @@ def make_dataset_dict(circle=None, hint=None):
         hint = "test " + inspect.currentframe().f_back.f_code.co_name
     if circle is None:
         filename = inspect.currentframe().f_back.f_code.co_filename
-        circle = filename.split("/")[-1].rsplit(".", 1)[0]
+        module = filename.split("/")[-1].rsplit(".", 1)[0]
+        circle = f"{get_user_name()}-{module}".replace("_", "-")
     dataset_dict = {
         "title": "{} {}".format(hint, time.time()),
         "private": True,
diff --git a/tests/test_dcserv.py b/tests/test_dcserv.py
index 6c3db05..c9ae2de 100644
--- a/tests/test_dcserv.py
+++ b/tests/test_dcserv.py
@@ -23,7 +23,7 @@ def test_access_public_data():
     assert res is True
 
 
-def test_access_private_data():
+def test_access_private_data(monkeypatch):
     """Upload a private dataset and try to access it"""
     # create some metadata
     dataset_dict = make_dataset_dict()
@@ -92,7 +92,10 @@ def test_access_private_data():
                            0.011666297,
                            atol=0, rtol=1e-5)
 
-    # Try to access the private dataset as a public user
+    # Try to access the private dataset as a public user. dclab remembers
+    # all API keys used in this process, so we have to forget them first.
+    monkeypatch.setattr(dclab.rtdc_dataset.fmt_dcor.api.APIHandler,
+                        "api_keys", [])
     with pytest.raises(dclab.rtdc_dataset.fmt_dcor.api.DCORAccessError):
         dclab.new_dataset(res_id, host=api.server, dcserv_api_version=2)