Fix pdb selftests on Python 3.13

Python 3.13 makes pdb break on the breakpoint() call,
rather than on the next line:
https://docs.python.org/3/whatsnew/3.13.html#pdb

Also runs the pdb tests on Python 3.13 in CI.
See #12884 for a more proper solution for that.

Fixes #12497

.github/workflows/test.yml

@@ -147,7 +147,7 @@ jobs:
           - name: "ubuntu-py313"
             python: "3.13-dev"
             os: ubuntu-latest
-            tox_env: "py313"
+            tox_env: "py313-pexpect"
             use_coverage: true
           - name: "ubuntu-pypy3"
             python: "pypy-3.9"

changelog/12497.contrib.rst

@@ -0,0 +1 @@
+Fixed two failing pdb-related tests on Python 3.13.

testing/test_debugging.py

@@ -771,9 +771,13 @@ class TestPDB:
             x = 5
         """
         )
+        if sys.version_info[:2] >= (3, 13):
+            break_line = "pytest.set_trace()"
+        else:
+            break_line = "x = 5"
         child = pytester.spawn(f"{sys.executable} {p1}")
-        child.expect("x = 5")
-        child.expect("Pdb")
+        child.expect_exact(break_line)
+        child.expect_exact("Pdb")
         child.sendeof()
         self.flush(child)
 
@@ -788,9 +792,13 @@ class TestPDB:
                 pass
         """
         )
+        if sys.version_info[:2] >= (3, 13):
+            break_line = "pytest.set_trace()"
+        else:
+            break_line = "x = 5"
         child = pytester.spawn_pytest(str(p1))
-        child.expect("x = 5")
-        child.expect("Pdb")
+        child.expect_exact(break_line)
+        child.expect_exact("Pdb")
         child.sendeof()
         self.flush(child)