test_c.py cannot import testing.support

src/c/test_c.py

@@ -6,7 +6,6 @@
 
 import pytest
 import sys
-import testing.support
 import typing as t
 
 is_musl = False
@@ -3407,9 +3406,14 @@ def test_bitfield_as_ppc_gcc():
 
 
 def buffer_warning(cdata):
-    testing.support.skip_if_multithreaded()
-
+    import threading
     import warnings
+
+    # warnings.catch_warnings() is not currently thread-safe, so skip the
+    # remainder of this test if running with `pytest-run-parallel`.
+    if threading.current_thread() != threading.main_thread():
+        pytest.skip("cannot run in a secondary thread")
+
     buf = buffer(cdata)
     bytes = len(buf)
     with warnings.catch_warnings(record=True) as w:

testing/support.py

@@ -1,5 +1,4 @@
 import sys, os
-import pytest
 from cffi._imp_emulation import load_dynamic
 
 if sys.version_info < (3,):
@@ -98,12 +97,6 @@ def typeof_disabled(*args, **kwds):
     return module.lib
 
 
-def skip_if_multithreaded():
-    import threading
-    if threading.current_thread() != threading.main_thread():
-        pytest.skip("cannot run in a secondary thread")
-
-
 # For testing, we call gcc with "-Werror".  This is fragile because newer
 # versions of gcc are always better at producing warnings, particularly for
 # auto-generated code.  We need here to adapt and silence them as needed.