From c851aa8a949524b35f72c82b45a52353aa3c0558 Mon Sep 17 00:00:00 2001
From: Ran Benita <ran@unusedvar.com>
Date: Sun, 28 Apr 2024 14:17:54 +0300
Subject: [PATCH] testing: allow to instantiate an empty AsyncTestCase
`unittest.TestCase` has a feature where it allows instantiating
`MyTestClass()` with the default method name `runTest` even if a
`runTest` method doesn't actually exist. This is documented in
`TestCase`'s docs under "Changed in version 3.2"[0].
Since version 8.2, pytest relies on this, and started breaking on
Tornado's `AsyncTestCase`[1].
Change `AsyncTestCase` to allow empty instatiation, by matching the
upstream code.
[0] https://docs.python.org/3/library/unittest.html#unittest.TestCase
[1] https://github.com/pytest-dev/pytest/issues/12263
---
tornado/test/testing_test.py | 9 +++++++++
tornado/testing.py | 12 +++++++++++-
2 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/tornado/test/testing_test.py b/tornado/test/testing_test.py
index 0429feee83..8e2b8db428 100644
--- a/tornado/test/testing_test.py
+++ b/tornado/test/testing_test.py
@@ -61,6 +61,15 @@ def test_subsequent_wait_calls(self):
self.io_loop.add_timeout(self.io_loop.time() + 0.2, self.stop)
self.wait(timeout=0.4)
+ def test_empty_instantation_is_allowed(self):
+ """
+ Test that empty instatiation of an AsyncTestCase is allowed.
+
+ unittest.TestCase docs guarantee this working, and pytest's unittest
+ support relies on it.
+ """
+ AsyncTestCaseTest()
+
class LeakTest(AsyncTestCase):
def tearDown(self):
diff --git a/tornado/testing.py b/tornado/testing.py
index bdbff87bc3..9455411a6d 100644
--- a/tornado/testing.py
+++ b/tornado/testing.py
@@ -177,7 +177,17 @@ def __init__(self, methodName: str = "runTest") -> None:
# the test will silently be ignored because nothing will consume
# the generator. Replace the test method with a wrapper that will
# make sure it's not an undecorated generator.
- setattr(self, methodName, _TestMethodWrapper(getattr(self, methodName)))
+ try:
+ test_method = getattr(self, methodName)
+ except AttributeError:
+ if methodName != "runTest":
+ # We allow instantiation with no explicit method name
+ # but not an *incorrect* or missing method name.
+ raise ValueError(
+ "no such test method in %s: %s" % (self.__class__, methodName)
+ )
+ else:
+ setattr(self, methodName, _TestMethodWrapper(test_method))
# Not used in this class itself, but used by @gen_test
self._test_generator = None # type: Optional[Union[Generator, Coroutine]]