Merge pull request #3720 from aknrdureegaesr/test_helper_improvement

Fix chdir leaking on error out of cd-contextmanager of tests/helper.py.

tests/helper.py

@@ -30,9 +30,11 @@
 @contextmanager
 def cd(path):
     old_dir = os.getcwd()
-    os.chdir(path)
-    yield
-    os.chdir(old_dir)
+    try:
+        os.chdir(path)
+        yield
+    finally:
+        os.chdir(old_dir)
 
 
 class FakeSite:

tests/test_test_helper.py

@@ -0,0 +1,22 @@
+import os
+
+from .helper import cd
+
+
+class SomeTestError(Exception):
+    """An arbitrary error to be thrown by the test."""
+    pass
+
+
+def test_test_helper():
+    """Check that the cd test helper duly resets the directory even in spite of an error."""
+    old_dir = os.getcwd()
+    exception_seen = False
+    try:
+        with cd(".."):
+            raise SomeTestError("Just raising an exception, as failing tests sometimes do.")
+    except SomeTestError:
+        now_dir = os.getcwd()
+        assert old_dir == now_dir
+        exception_seen = True
+    assert exception_seen