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diff --git a/gnu/packages/aux-files/python/pytest_guix.py b/gnu/packages/aux-files/python/pytest_guix.py
new file mode 100644
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+++ b/gnu/packages/aux-files/python/pytest_guix.py
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+# GNU Guix --- Functional package management for GNU
+# Copyright © 2025 Nicolas Graves <ngraves@ngraves.fr>
+#
+# This file is part of GNU Guix.
+#
+# GNU Guix is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or (at
+# your option) any later version.
+#
+# GNU Guix is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+import importlib.util
+
+
+def pytest_addoption(parser):
+    """Add stub options to be ignored by pytest.
+
+    More precisely, inject all options provided in .pytest_guix_options.json,
+    except options whose plugin is indeed installed.
+
+    For example, if the json file records --cov:
+      if the pytest_cov module is installed, its --cov will be used.
+      otherwise, --cov is ignored (read by this parser, but nothing is done
+      with it).
+
+    This allows to remove development packages, which are not required at build
+    time while at the same time avoiding the need to adjust test options in
+    pyproject.toml or other configuration files.
+    """
+    plugin_options = {
+        "cov": [
+            "--cov",
+            "--cov-reset",
+            "--cov-report",
+            "--cov-config",
+            "--no-cov-on-fail",
+            "--no-cov",
+            "--cov-fail-under",
+            "--cov-append",
+            "--cov-branch",
+            "--cov-context",
+        ],
+        "mypy": ["--mypy", "--mypy-config-file", "--mypy-ignore-missing-imports"],
+        "isort": ["--isort"],
+        "flake8": ["--flake8"],
+        "black": ["--black"],
+        "flakes": ["--flakes"],
+        "pep8": ["--pep8"],
+        "html": ["--html", "--self-contained-html", "--css"],
+    }
+
+    group = parser.getgroup(
+        "guix", "Options ignored by the Guix pyproject-build-system"
+    )
+
+    # Only add options for plugins that are not present.
+    for key, options in plugin_options.items():
+        if importlib.util.find_spec(f"pytest_{key}") is None:
+            # Plugin not found, add stub options
+            for option in options:
+                group.addoption(option, action="append", nargs="?")