From 3444d35c540c635401f92db724d004e2a7d20920 Mon Sep 17 00:00:00 2001
From: Babak Keyvani <babak@keyvani.com>
Date: Sat, 30 Apr 2022 17:56:36 -0600
Subject: [PATCH] improve `pytest.raises`

---
 AUTHORS                        | 1 +
 changelog/8646.improvments.rst | 2 ++
 src/_pytest/python_api.py      | 7 +++++++
 testing/python/raises.py       | 4 ++++
 4 files changed, 14 insertions(+)
 create mode 100644 changelog/8646.improvments.rst

diff --git a/AUTHORS b/AUTHORS
index 1a8c5306f..86a814a13 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -44,6 +44,7 @@ Aron Coyle
 Aron Curzon
 Aviral Verma
 Aviv Palivoda
+Babak Keyvani
 Barney Gale
 Ben Gartner
 Ben Webb
diff --git a/changelog/8646.improvments.rst b/changelog/8646.improvments.rst
new file mode 100644
index 000000000..9691c1434
--- /dev/null
+++ b/changelog/8646.improvments.rst
@@ -0,0 +1,2 @@
+Improve :py:func:`pytest.raises`. Previously passing an empty tuple would give a confusing
+error. We now raise immediately with a more helpful message.
diff --git a/src/_pytest/python_api.py b/src/_pytest/python_api.py
index 5fa219619..410877c88 100644
--- a/src/_pytest/python_api.py
+++ b/src/_pytest/python_api.py
@@ -899,6 +899,13 @@ def raises(
     """
     __tracebackhide__ = True
 
+    if expected_exception == ():
+        raise ValueError(
+            "Passing expected_exception=() is an error, because it's impossible to "
+            "raise an exception which is not an instance of any type. Raising exceptions "
+            "is already understood as failing the test, so you don't need any special "
+            "code to say 'this should never raise an exception'."
+        )
     if isinstance(expected_exception, type):
         excepted_exceptions: Tuple[Type[E], ...] = (expected_exception,)
     else:
diff --git a/testing/python/raises.py b/testing/python/raises.py
index 112dec06c..e1680623a 100644
--- a/testing/python/raises.py
+++ b/testing/python/raises.py
@@ -19,6 +19,10 @@ class TestRaises:
         excinfo = pytest.raises(ValueError, int, "hello")
         assert "invalid literal" in str(excinfo.value)
 
+    def test_raises_does_not_allow_empty_tuple(self):
+        with pytest.raises(ValueError):
+            pytest.raises(expected_exception=())
+
     def test_raises_callable_no_exception(self) -> None:
         class A:
             def __call__(self):