Fix AttributeError bug in TestCaseFunction.teardown by creating TestCaseFunction._testcase as attribute of class with a None default.

changelog/3788.bugfix.rst

@@ -0,0 +1 @@
+Fix AttributeError bug in TestCaseFunction.teardown by creating TestCaseFunction._testcase as attribute of class with a None default.

src/_pytest/unittest.py

@@ -69,6 +69,7 @@ class UnitTestCase(Class):
 class TestCaseFunction(Function):
     nofuncargs = True
     _excinfo = None
+    _testcase = None
 
     def setup(self):
         self._testcase = self.parent.obj(self.name)

testing/test_unittest.py

@@ -989,3 +989,24 @@ def test_usefixtures_marker_on_unittest(base, testdir):
 
     result = testdir.runpytest("-s")
     result.assert_outcomes(passed=2)
+
+
+def test_testcase_handles_init_exceptions(testdir):
+    """
+    Regression test to make sure exceptions in the __init__ method are bubbled up correctly.
+    See https://github.com/pytest-dev/pytest/issues/3788
+    """
+    testdir.makepyfile(
+        """
+        from unittest import TestCase
+        import pytest
+        class MyTestCase(TestCase):
+            def __init__(self, *args, **kwargs):
+                raise Exception("should raise this exception")            
+            def test_hello(self):
+                pass
+    """
+    )
+    result = testdir.runpytest()
+    assert "should raise this exception" in result.stdout.str()
+    assert "ERROR at teardown of MyTestCase.test_hello" not in result.stdout.str()