fix(pytest): fix double yield problem in isolation fixture [APE-1353] (…

…ApeWorX#1642)

src/ape/pytest/fixtures.py

@@ -94,12 +94,16 @@ def _isolation(self) -> Iterator[None]:
             snapshot_id = None
 
         if self._track_transactions:
+            did_yield = False
             try:
                 with self.receipt_capture:
                     yield
+                    did_yield = True
 
             except BlockNotFoundError:
-                yield
+                if not did_yield:
+                    # Prevent double yielding.
+                    yield
 
         else:
             yield

tests/functional/test_fixtures.py

@@ -0,0 +1,31 @@
+import pytest
+
+from ape.exceptions import BlockNotFoundError
+from ape.pytest.fixtures import PytestApeFixtures
+
+
+@pytest.fixture
+def receipt_capture(mocker):
+    return mocker.MagicMock()
+
+
+@pytest.fixture
+def fixtures(mocker, receipt_capture):
+    return PytestApeFixtures(mocker.MagicMock(), receipt_capture)
+
+
+@pytest.fixture
+def isolation(fixtures):
+    return fixtures._isolation()
+
+
+def test_isolation(isolation, receipt_capture):
+    # Set up receipt capture to fail on __exit__
+    # AFTER the yield statement. There was a bug
+    # where we got a double-yield in this situation.
+
+    receipt_capture.__exit__.side_effect = BlockNotFoundError(0)
+
+    assert next(isolation) is None
+    with pytest.raises(StopIteration):
+        next(isolation)