Issue #25108: Backported tests for traceback functions print_stack(),

format_stack(), and extract_stack() called without arguments.

Lib/test/test_traceback.py

@@ -242,6 +242,31 @@ class TracebackFormatTests(unittest.TestCase):
 
         self.assertEqual(ststderr.getvalue(), "".join(stfmt))
 
+    def test_print_stack(self):
+        def prn():
+            traceback.print_stack()
+        with captured_output("stderr") as stderr:
+            prn()
+        lineno = prn.__code__.co_firstlineno
+        self.assertEqual(stderr.getvalue().splitlines()[-4:], [
+            '  File "%s", line %d, in test_print_stack' % (__file__, lineno+3),
+            '    prn()',
+            '  File "%s", line %d, in prn' % (__file__, lineno+1),
+            '    traceback.print_stack()',
+        ])
+
+    def test_format_stack(self):
+        def fmt():
+            return traceback.format_stack()
+        result = fmt()
+        lineno = fmt.__code__.co_firstlineno
+        self.assertEqual(result[-2:], [
+            '  File "%s", line %d, in test_format_stack\n'
+            '    result = fmt()\n' % (__file__, lineno+2),
+            '  File "%s", line %d, in fmt\n'
+            '    return traceback.format_stack()\n' % (__file__, lineno+1),
+        ])
+
 
 cause_message = (
     "\nThe above exception was the direct cause "
@@ -443,6 +468,16 @@ class MiscTracebackCases(unittest.TestCase):
         # Local variable dict should now be empty.
         self.assertEqual(len(inner_frame.f_locals), 0)
 
+    def test_extract_stack(self):
+        def extract():
+            return traceback.extract_stack()
+        result = extract()
+        lineno = extract.__code__.co_firstlineno
+        self.assertEqual(result[-2:], [
+            (__file__, lineno+2, 'test_extract_stack', 'result = extract()'),
+            (__file__, lineno+1, 'extract', 'return traceback.extract_stack()'),
+        ])
+
 
 def test_main():
     run_unittest(__name__)