add test for _ExceptionInfo (and fix it)

src/trio/_tests/test_testing_raisesgroup.py

@@ -2,10 +2,12 @@
 
 import re
 import sys
+from types import TracebackType
 from typing import TYPE_CHECKING
 
 import pytest
 
+import trio
 from trio.testing import Matcher, RaisesGroup
 
 # TODO: make a public export
@@ -195,6 +197,19 @@ def check_errno_is_5(e: OSError) -> bool:
             raise ExceptionGroup("", (OSError(6, ""),))
 
 
+def test__ExceptionInfo(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(
+        trio.testing._raises_group,
+        "ExceptionInfo",
+        trio.testing._raises_group._ExceptionInfo,
+    )
+    with trio.testing.RaisesGroup(ValueError) as excinfo:
+        raise ExceptionGroup("", (ValueError("hello"),))
+    assert excinfo.type is ExceptionGroup
+    assert excinfo.value.exceptions[0].args == ("hello",)
+    assert isinstance(excinfo.tb, TracebackType)
+
+
 if TYPE_CHECKING:
     # getting the typing working satisfactory is very tricky
     # but with RaisesGroup being seen as a subclass of BaseExceptionGroup

src/trio/testing/_raises_group.py

@@ -32,7 +32,7 @@ class _ExceptionInfo(Generic[E]):
     _excinfo: tuple[type[E], E, TracebackType] | None
 
     def __init__(self, excinfo: tuple[type[E], E, TracebackType] | None):
-        self._exc_info = excinfo
+        self._excinfo = excinfo
 
     def fill_unfilled(self, exc_info: tuple[type[E], E, TracebackType]) -> None:
         """Fill an unfilled ExceptionInfo created with ``for_later()``."""
@@ -44,6 +44,30 @@ def for_later(cls) -> _ExceptionInfo[E]:
         """Return an unfilled ExceptionInfo."""
         return cls(None)
 
+    @property
+    def type(self) -> type[E]:
+        """The exception class."""
+        assert (
+            self._excinfo is not None
+        ), ".type can only be used after the context manager exits"
+        return self._excinfo[0]
+
+    @property
+    def value(self) -> E:
+        """The exception value."""
+        assert (
+            self._excinfo is not None
+        ), ".value can only be used after the context manager exits"
+        return self._excinfo[1]
+
+    @property
+    def tb(self) -> TracebackType:
+        """The exception raw traceback."""
+        assert (
+            self._excinfo is not None
+        ), ".tb can only be used after the context manager exits"
+        return self._excinfo[2]
+
 
 # this may bite users with type checkers not using pytest, but that should
 # be rare and give quite obvious errors in tests trying to do so.
@@ -53,7 +77,7 @@ def for_later(cls) -> _ExceptionInfo[E]:
 else:
     try:
         from pytest import ExceptionInfo
-    except ImportError:
+    except ImportError:  # pragma: no cover
         ExceptionInfo = _ExceptionInfo