From c5cb5f11dc7b759e41332ceb2348d01f82b83475 Mon Sep 17 00:00:00 2001
From: Eric Wieser <wieser.eric@gmail.com>
Date: Fri, 28 Aug 2020 18:35:39 +0100
Subject: [PATCH] Fix sympy.testing.pytest.raises to behave like pytest.raises

Code written as `assert raises(...)` would pass in pytest and fail in sympy, because sympy was not returning an appropriate object from `raises`.
---
 sympy/multipledispatch/tests/test_core.py       | 4 +---
 sympy/multipledispatch/tests/test_dispatcher.py | 8 +-------
 sympy/testing/pytest.py                         | 6 +++++-
 3 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/sympy/multipledispatch/tests/test_core.py b/sympy/multipledispatch/tests/test_core.py
index d5df0bd605a7..c8e60caf5f0d 100644
--- a/sympy/multipledispatch/tests/test_core.py
+++ b/sympy/multipledispatch/tests/test_core.py
@@ -2,7 +2,7 @@
 
 from sympy.multipledispatch import dispatch
 from sympy.multipledispatch.conflict import AmbiguityWarning
-from sympy.testing.pytest import raises, XFAIL, warns
+from sympy.testing.pytest import raises, warns
 from functools import partial
 
 test_namespace = dict()  # type: Dict[str, Any]
@@ -11,7 +11,6 @@
 dispatch = partial(dispatch, namespace=test_namespace)
 
 
-@XFAIL
 def test_singledispatch():
     @dispatch(int)
     def f(x): # noqa:F811
@@ -66,7 +65,6 @@ def f(x): # noqa:F811
     assert f(C()) == 'a'
 
 
-@XFAIL
 def test_inheritance_and_multiple_dispatch():
     @dispatch(A, A)
     def f(x, y): # noqa:F811
diff --git a/sympy/multipledispatch/tests/test_dispatcher.py b/sympy/multipledispatch/tests/test_dispatcher.py
index 28732cae068a..b980a8b19afc 100644
--- a/sympy/multipledispatch/tests/test_dispatcher.py
+++ b/sympy/multipledispatch/tests/test_dispatcher.py
@@ -1,7 +1,7 @@
 from sympy.multipledispatch.dispatcher import (Dispatcher, MDNotImplementedError,
                                          MethodDispatcher, halt_ordering,
                                          restart_ordering)
-from sympy.testing.pytest import raises, XFAIL, warns
+from sympy.testing.pytest import raises, warns
 
 
 def identity(x):
@@ -88,7 +88,6 @@ def on_ambiguity(dispatcher, amb):
     assert ambiguities[0]
 
 
-@XFAIL
 def test_raise_error_on_non_class():
     f = Dispatcher('f')
     assert raises(TypeError, lambda: f.add((1,), inc))
@@ -165,7 +164,6 @@ def two(x, y):
     assert 'x - y' in f._source(1.0, 1.0)
 
 
-@XFAIL
 def test_source_raises_on_missing_function():
     f = Dispatcher('f')
 
@@ -197,13 +195,11 @@ def func(*args):
     assert set(f.ordering) == {(int, object), (object, int)}
 
 
-@XFAIL
 def test_no_implementations():
     f = Dispatcher('f')
     assert raises(NotImplementedError, lambda: f('hello'))
 
 
-@XFAIL
 def test_register_stacking():
     f = Dispatcher('f')
 
@@ -238,7 +234,6 @@ class MyList(list):
     assert f.dispatch(int, int) is add
 
 
-@XFAIL
 def test_not_implemented():
     f = Dispatcher('f')
 
@@ -259,7 +254,6 @@ def _(x):
     assert raises(NotImplementedError, lambda: f(1, 2))
 
 
-@XFAIL
 def test_not_implemented_error():
     f = Dispatcher('f')
 
diff --git a/sympy/testing/pytest.py b/sympy/testing/pytest.py
index 174fc590a035..d681775bb342 100644
--- a/sympy/testing/pytest.py
+++ b/sympy/testing/pytest.py
@@ -34,6 +34,10 @@
     # Not using pytest so define the things that would have been imported from
     # there.
 
+    class _ExceptionInfo:
+        # pytest would implement this
+        pass
+
     def raises(expectedException, code=None):
         """
         Tests that ``code`` raises the exception ``expectedException``.
@@ -93,7 +97,7 @@ def raises(expectedException, code=None):
             try:
                 code()
             except expectedException:
-                return
+                return _ExceptionInfo()
             raise Failed("DID NOT RAISE")
         elif isinstance(code, str):
             raise TypeError(