fix flaky tests

.github/workflows/main.yml

@@ -249,7 +249,7 @@ jobs:
     - name: Install dependencies
       run: uv pip install . --group test
     - name: Install Docutils' HEAD
-      run: uv pip install "docutils @ git+https://repo.or.cz/docutils.git#subdirectory=docutils"
+      run: uv pip install "docutils @ git+https://github.com/docutils/docutils.git#subdirectory=docutils"
     - name: Test with pytest
       run: python -m pytest -n logical --dist=worksteal -vv
       env:
@@ -313,7 +313,7 @@ jobs:
     - name: Install dependencies
       run: uv pip install . --group test
     - name: Install Docutils' HEAD
-      run: uv pip install "docutils @ git+https://repo.or.cz/docutils.git#subdirectory=docutils"
+      run: uv pip install "docutils @ git+https://github.com/docutils/docutils.git#subdirectory=docutils"
     - name: Test with pytest
       run: python -m pytest -vv --durations 25
       env:

CHANGES.rst

@@ -41,6 +41,10 @@ Release 9.1.1 (released Oct 19, 2026)
 Bugs fixed
 ----------
 
+* #14690: Fix test isolation issues caused by shared test directories and
+  inherited ``NO_COLOR`` and ``NO_COLOUR`` environment variables.
+  Patch by Kilian Paul
+
 * #14465: LaTeX: PDF build crash since LaTeX June 2026 release if tables are
   styled with ``'colorrows'`` (which is the default).
   Patch by Jean-François B.

tests/roots/test-linkcheck-case-check/conf.py

@@ -1 +1,3 @@
-linkcheck_timeout = 0.25
+# Short but not too short: CI runners with few CPUs can stall
+# a local test server for a few hundred milliseconds under load.
+linkcheck_timeout = 2

tests/test_builders/test_build_html_5_output.py

@@ -551,7 +551,7 @@ def test_html5_output(
     check_xpath(cached_etree_parse(app.outdir / fname), fname, path, check)
 
 
-@pytest.mark.sphinx('html', testroot='markup-rubric')
+@pytest.mark.sphinx('html', testroot='markup-rubric', srcdir='markup-rubric-html')
 def test_html5_rubric(app: SphinxTestApp) -> None:
     def insert_invalid_rubric_heading_level(
         app: SphinxTestApp,

tests/test_builders/test_build_latex.py

@@ -2284,7 +2284,7 @@ def test_one_parameter_per_line_without_trailing_comma(app: SphinxTestApp) -> No
     assert r'\sphinxparam{\DUrole{n}{f}}}}' in result
 
 
-@pytest.mark.sphinx('latex', testroot='markup-rubric')
+@pytest.mark.sphinx('latex', testroot='markup-rubric', srcdir='markup-rubric-latex')
 def test_latex_rubric(app: SphinxTestApp) -> None:
     app.build()
     content = (app.outdir / 'test.tex').read_text(encoding='utf8')

tests/test_builders/test_build_linkcheck.py

@@ -1461,20 +1461,22 @@ class CapitalisePathHandler(BaseHTTPRequestHandler):
 
     protocol_version = 'HTTP/1.1'
 
-    def do_GET(self) -> None:
+    def _respond(self) -> None:
         if self.path.islower():
             # Redirect lowercase paths to uppercase versions
             self.send_response(301, 'Moved Permanently')
             self.send_header('Location', self.path.upper())
-            self.send_header('Content-Length', '0')
-            self.end_headers()
         else:
             # Serve uppercase paths
-            content = b'ok\n\n'
             self.send_response(200, 'OK')
-            self.send_header('Content-Length', str(len(content)))
-            self.end_headers()
-            self.wfile.write(content)
+        self.send_header('Content-Length', '0')
+        self.end_headers()
+
+    def do_GET(self) -> None:
+        self._respond()
+
+    def do_HEAD(self) -> None:
+        self._respond()
 
 
 @pytest.mark.sphinx(

tests/test_builders/test_build_manpage.py

@@ -100,7 +100,7 @@ def test_default_man_pages() -> None:
     assert default_man_pages(config) == expected
 
 
-@pytest.mark.sphinx('man', testroot='markup-rubric')
+@pytest.mark.sphinx('man', testroot='markup-rubric', srcdir='markup-rubric-man')
 def test_rubric(app: SphinxTestApp) -> None:
     app.build()
     content = (app.outdir / 'projectnamenotset.1').read_text(encoding='utf8')

tests/test_builders/test_build_texinfo.py

@@ -44,7 +44,7 @@ def test_texinfo(app: SphinxTestApp) -> None:
         raise AssertionError(msg) from exc
 
 
-@pytest.mark.sphinx('texinfo', testroot='markup-rubric')
+@pytest.mark.sphinx('texinfo', testroot='markup-rubric', srcdir='markup-rubric-texinfo')
 def test_texinfo_rubric(app: SphinxTestApp) -> None:
     app.build()