---
 setup.cfg         |    4 +++-
 tests/test_doi.py |    4 ++++
 2 files changed, 7 insertions(+), 1 deletion(-)

--- a/setup.cfg
+++ b/setup.cfg
@@ -5,7 +5,9 @@ universal = 1
 exclude = docs
 
 [tool:pytest]
-collect_ignore = ['setup.py']
+markers =
+    net: marks tests that call use the net (using the URL endpoint, deselect with '-k "not net"')
+
 
 [mypy]
 disallow_redefinition = True
--- a/tests/test_doi.py
+++ b/tests/test_doi.py
@@ -3,6 +3,8 @@
 import os
 from pkg_resources import parse_version
 
+import pytest
+
 from doi import (
     validate_doi, find_doi_in_text, __version__, pdf_to_doi,
     get_real_url_from_doi
@@ -14,6 +16,7 @@ def test_valid_version() -> None:
     assert parse_version(__version__) >= parse_version("0.1.0")
 
 
+@pytest.mark.net
 def test_validate_doi() -> None:
     data = [
         ('10.1063/1.5081715',
@@ -38,6 +41,7 @@ def test_validate_doi() -> None:
             assert str(e) == 'HTTP 404: DOI not found'
 
 
+@pytest.mark.net
 def test_get_real_url_from_doi() -> None:
     data = [
         ('10.1016/S0009-2614(97)04014-1',