Issue #19440: Clean up test_capi

Lib/test/test_capi.py

 # Run the _testcapi module tests (tests for the Python/C API):  by defn,
 # these are all functions _testcapi exports whose name begins with 'test_'.
 
-from __future__ import with_statement
 import os
 import pickle
 import random
@@ -416,18 +415,13 @@ class TestThreadState(unittest.TestCase):
         t.start()
         t.join()
 
-
-def test_main():
-    support.run_unittest(CAPITest, TestPendingCalls, Test6012,
-                         EmbeddingTests, SkipitemTest, TestThreadState,
-                         SubinterpreterTest)
-
-    for name in dir(_testcapi):
-        if name.startswith('test_'):
-            test = getattr(_testcapi, name)
-            if support.verbose:
-                print("internal", name)
-            test()
+class Test_testcapi(unittest.TestCase):
+    def test__testcapi(self):
+        for name in dir(_testcapi):
+            if name.startswith('test_'):
+                with self.subTest("internal", name=name):
+                    test = getattr(_testcapi, name)
+                    test()
 
 if __name__ == "__main__":
-    test_main()
+    unittest.main()

Misc/NEWS

@@ -213,6 +213,10 @@ Library
 Tests
 -----
 
+- Issue #19440: Clean up test_capi by removing an unnecessary __future__
+  import, converting from test_main to unittest.main, and running the
+  _testcapi module tests as subTests of a unittest TestCase method.
+
 - Issue #19378: the main dis module tests are now run with both stdout
   redirection *and* passing an explicit file parameter