Make --pdb work with subTest().

[Lucidiot]

With a test case that contains a TestCase.subTest call, a failure or error of a subtest does not cause pdb or ipdb to open when running manage.py test --pdb.

from django.test import TestCase

class TestSomething(TestCase):
    def test_something(self):
        with self.subTest(a=1):
            raise ZeroDivisionError("oh snap!")

λ ./manage.py test --pdb
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
...
======================================================================
ERROR: test_something (demo.app.tests.test_something.TestSomething) (a=1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/.../tests/test_something.py", line 6, in test_something
    raise ZeroDivisionError("oh snap!")
ZeroDivisionError: oh snap!

----------------------------------------------------------------------
Ran 1 tests in 0.154s

FAILED (errors=1)
Destroying test database for alias 'default'...

It seems that CPython has some ​special handling code for subtest results that does not use TestResult.addError or TestResult.addFailure, and the PDBDebugResult ​only implements those. Note that --debug-sql does work with subtests because the DebugSQLTextTestResult ​supports subtests.

[Mariusz Felisiak]

Thanks for the report. It seems it's enough to call debug() 🤔, e.g.

    def addSubTest(self, test, subtest, err):
        if err is not None:
            self.debug(err)
        super().addSubTest(test, subtest, err)

Would you like to provide a patch?

[Abhyudai]

for what it is worth, only adding the call to debug() didn't work, at least on my end. i will try to look more into this.

[Lucidiot]

Sorry for the delay! Adding a self.debug call as in the code block above does seem to work on my machine, at least when hastily adding it by editing my site-packages (don't try this at home). I could maybe provide a patch, and Abhyudai can test it to see if something is truly missing?

[Abhyudai]

Just to be on the same page, this is the diff that is being talked about, no?

diff --git a/django/test/runner.py b/django/test/runner.py
index 225bc19b09..9ea67ce4b6 100644
--- a/django/test/runner.py
+++ b/django/test/runner.py
@@ -275,6 +275,7 @@ failure and get a correct traceback.
             self.check_picklable(test, err)
             self.check_subtest_picklable(test, subtest)
             self.events.append(('addSubTest', self.test_index, subtest, err))
+            self.debug(err)
         super().addSubTest(test, subtest, err)
 
     def addSuccess(self, test):

[Lucidiot]

No, I added the method to the PDBDebugResult directly:

diff --git a/django/test/runner.py b/django/test/runner.py
index 225bc19b09..b4dd974d57 100644
--- a/django/test/runner.py
+++ b/django/test/runner.py
@@ -107,6 +107,10 @@ class PDBDebugResult(unittest.TextTestResult):
         super().addFailure(test, err)
         self.debug(err)
 
+    def addSubTest(self, test, subtest, err):
+        super().addSubTest(test, subtest, err)
+        self.debug(err)
+
     def debug(self, error):
         self._restoreStdout()
         self.buffer = False

[Abhyudai]

yes, it seems to work. thanks

​pull-request

[GitHub <noreply@…>]

In 7872971d:

Fixed #33149 -- Made test runner --pdb option work with subTest().

Thanks Lucidot for the report and Mariusz Felisiak for the initial
patch.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 44d11e5b:

[4.0.x] Fixed #33149 -- Made test runner --pdb option work with subTest().

Thanks Lucidot for the report and Mariusz Felisiak for the initial
patch.
Backport of 7872971dfbb818177168e64c24a933e48ce01206 from main