Fixed issue shadowing error when missing argument on teardown_method

When the method argument is missing on teardown_method, the traceback is
100% internal to pytest, which with default options get pruned. Then
that traceback is empty, leading to a new exception as a traceback shall
not be empty.

This PR fixes that issue by pushing back the last stack on the
traceback, when the stacktrace is empty after pruning. Then the output
is still pruned, but gives meaningful information with the item where it
failed on the stack.

* fixes issue #1604

Signed-off-by: Guyzmo <guyzmo+github@m0g.net>

AUTHORS

@@ -91,3 +91,4 @@ Thomas Grainger
 Tom Viner
 Trevor Bekolay
 Wouter van Ackooy
+Bernard Pratz

CHANGELOG.rst

@@ -6,7 +6,8 @@
 * Text documents without any doctests no longer appear as "skipped".
   Thanks `@graingert`_ for reporting and providing a full PR (`#1580`_).
 
-*
+* Fix internal error issue when ``method`` argument is missing for 
+  ``teardown_method()``. Fixes (`#1605`_).
 
 *
 
@@ -15,6 +16,7 @@
   `@marscher`. Thanks `@nicoddemus` for his help.
 
 .. _#1580: https://github.com/pytest-dev/pytest/issues/1580
+.. _#1605: https://github.com/pytest-dev/pytest/issues/1605
 
 .. _@graingert: https://github.com/graingert
 

_pytest/main.py

@@ -392,7 +392,10 @@ class Node(object):
         if self.config.option.fulltrace:
             style="long"
         else:
+            tb = _pytest._code.Traceback([excinfo.traceback[-1]])
             self._prunetraceback(excinfo)
+            if len(excinfo.traceback) == 0:
+                excinfo.traceback = tb
             tbfilter = False  # prunetraceback already does it
             if style == "auto":
                 style = "long"

testing/test_runner.py

@@ -228,6 +228,39 @@ class BaseFunctionalTests:
         assert reps[5].nodeid.endswith("test_func")
         assert reps[5].failed
 
+    def test_exact_teardown_issue1206(self, testdir):
+        rec = testdir.inline_runsource("""
+            import pytest
+
+            class TestClass:
+                def teardown_method(self):
+                    pass
+
+                def test_method(self):
+                    assert True
+        """)
+        reps = rec.getreports("pytest_runtest_logreport")
+        print (reps)
+        assert len(reps) == 3
+        #
+        assert reps[0].nodeid.endswith("test_method")
+        assert reps[0].passed
+        assert reps[0].when == 'setup'
+        #
+        assert reps[1].nodeid.endswith("test_method")
+        assert reps[1].passed
+        assert reps[1].when == 'call'
+        #
+        assert reps[2].nodeid.endswith("test_method")
+        assert reps[2].failed
+        assert reps[2].when == "teardown"
+        assert reps[2].longrepr.reprcrash.message in (
+                # python3 error
+                'TypeError: teardown_method() takes 1 positional argument but 2 were given',
+                # python2 error
+                'TypeError: teardown_method() takes exactly 1 argument (2 given)'
+                )
+
     def test_failure_in_setup_function_ignores_custom_repr(self, testdir):
         testdir.makepyfile(conftest="""
             import pytest