diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index 0afc0fc..8935de1 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -10,7 +10,6 @@ on:
 
 jobs:
   build:
-
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
@@ -18,8 +17,6 @@ jobs:
         python-version: ["3.9", "3.10", "3.11"]
 
     steps:
-    - uses: actions/checkout@v4
-    - name: Set up Python ${{ matrix.python-version }}
       - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v3
@@ -37,5 +34,7 @@ jobs:
           # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
           flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
       - name: Test with pytest
+        env:
+          DEEPL_AUTH_KEY: ${{ secrets.DEEPL_AUTH_KEY }}
         run: |
           pytest
diff --git a/tests/conftest.py b/tests/conftest.py
index c5ae388..dda2ae3 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -177,6 +177,8 @@ def _make_deepl_client(server, auth_key=None, proxy=None):
 def translator(server):
     """Returns a deepl.Translator to use in all tests taking a parameter
     'translator'."""
+    if not server.is_mock_server and not server.auth_key:
+        pytest.skip("this test requires DEEPL_AUTH_KEY for real server usage")
     return _make_translator(server)
 
 
@@ -186,6 +188,8 @@ def translator(server):
 def deepl_client(server):
     """Returns a deepl.DeepLClient to use in all tests taking a parameter
     'deepl_client'."""
+    if not server.is_mock_server and not server.auth_key:
+        pytest.skip("this test requires DEEPL_AUTH_KEY for real server usage")
     return _make_deepl_client(server)
 
 
diff --git a/tests/test_cli.py b/tests/test_cli.py
index ad19975..704fb2a 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -19,6 +19,8 @@
 
 @pytest.fixture
 def runner(server):
+    if not server.is_mock_server and not server.auth_key:
+        pytest.skip("this test requires DEEPL_AUTH_KEY for real server usage")
     env = {
         "DEEPL_SERVER_URL": server.server_url,
         "DEEPL_AUTH_KEY": server.auth_key,
diff --git a/tests/test_general.py b/tests/test_general.py
index cf1afce..d8a057c 100644
--- a/tests/test_general.py
+++ b/tests/test_general.py
@@ -15,6 +15,8 @@
 import pytest
 import os
 
+TEST_AUTH_KEY = os.getenv("DEEPL_AUTH_KEY") or "test_auth_key"
+
 
 def test_version():
     assert "1.30.0" == deepl.__version__
@@ -141,7 +143,7 @@ def test_server_url_selected_based_on_auth_key(server):
 @patch("requests.adapters.HTTPAdapter.send")
 def test_user_agent(mock_send):
     mock_send.return_value = _build_test_response()
-    translator = deepl.Translator(os.environ["DEEPL_AUTH_KEY"])
+    translator = deepl.Translator(TEST_AUTH_KEY)
     translator.translate_text(example_text["EN"], target_lang="DA")
     ua_header = mock_send.call_args[0][0].headers["User-agent"]
     assert "requests/" in ua_header
@@ -152,9 +154,7 @@ def test_user_agent(mock_send):
 @patch("requests.adapters.HTTPAdapter.send")
 def test_user_agent_opt_out(mock_send):
     mock_send.return_value = _build_test_response()
-    translator = deepl.Translator(
-        os.environ["DEEPL_AUTH_KEY"], send_platform_info=False
-    )
+    translator = deepl.Translator(TEST_AUTH_KEY, send_platform_info=False)
     translator.translate_text(example_text["EN"], target_lang="DA")
     ua_header = mock_send.call_args[0][0].headers["User-agent"]
     assert "requests/" not in ua_header
@@ -167,7 +167,7 @@ def test_custom_user_agent(mock_send):
     mock_send.return_value = _build_test_response()
     old_user_agent = deepl.http_client.user_agent
     deepl.http_client.user_agent = "my custom user agent"
-    translator = deepl.Translator(os.environ["DEEPL_AUTH_KEY"])
+    translator = deepl.Translator(TEST_AUTH_KEY)
     translator.translate_text(example_text["EN"], target_lang="DA")
     ua_header = mock_send.call_args[0][0].headers["User-agent"]
     assert ua_header == "my custom user agent"
@@ -177,9 +177,9 @@ def test_custom_user_agent(mock_send):
 @patch("requests.adapters.HTTPAdapter.send")
 def test_user_agent_with_app_info(mock_send):
     mock_send.return_value = _build_test_response()
-    translator = deepl.Translator(
-        os.environ["DEEPL_AUTH_KEY"],
-    ).set_app_info("sample_python_plugin", "1.0.2")
+    translator = deepl.Translator(TEST_AUTH_KEY).set_app_info(
+        "sample_python_plugin", "1.0.2"
+    )
     translator.translate_text(example_text["EN"], target_lang="DA")
     ua_header = mock_send.call_args[0][0].headers["User-agent"]
     assert "requests/" in ua_header
@@ -192,7 +192,7 @@ def test_user_agent_with_app_info(mock_send):
 def test_user_agent_opt_out_with_app_info(mock_send):
     mock_send.return_value = _build_test_response()
     translator = deepl.Translator(
-        os.environ["DEEPL_AUTH_KEY"],
+        TEST_AUTH_KEY,
         send_platform_info=False,
     ).set_app_info("sample_python_plugin", "1.0.2")
     translator.translate_text(example_text["EN"], target_lang="DA")
@@ -208,7 +208,7 @@ def test_custom_user_agent_with_app_info(mock_send):
     mock_send.return_value = _build_test_response()
     old_user_agent = deepl.http_client.user_agent
     deepl.http_client.user_agent = "my custom user agent"
-    translator = deepl.Translator(os.environ["DEEPL_AUTH_KEY"]).set_app_info(
+    translator = deepl.Translator(TEST_AUTH_KEY).set_app_info(
         "sample_python_plugin", "1.0.2"
     )
     translator.translate_text(example_text["EN"], target_lang="DA")
@@ -222,7 +222,7 @@ def test_custom_user_agent_with_app_info(mock_send):
 def test_user_agent_exception(platform_mock, mock_send):
     mock_send.return_value = _build_test_response()
     platform_mock.side_effect = OSError("mocked test exception")
-    translator = deepl.Translator(os.environ["DEEPL_AUTH_KEY"])
+    translator = deepl.Translator(TEST_AUTH_KEY)
     translator.translate_text(example_text["EN"], target_lang="DA")
     ua_header = mock_send.call_args[0][0].headers["User-agent"]
     assert "deepl-python" in ua_header
diff --git a/tests/test_translate_text.py b/tests/test_translate_text.py
index 658e7a5..93d4c0d 100644
--- a/tests/test_translate_text.py
+++ b/tests/test_translate_text.py
@@ -124,6 +124,8 @@ def test_invalid_language(translator):
 
 
 def test_skip_language_check(server):
+    if not server.is_mock_server and not server.auth_key:
+        pytest.skip("this test requires DEEPL_AUTH_KEY for real server usage")
     translator = deepl.Translator(
         server.auth_key, server_url=server.server_url, skip_language_check=True
     )