Fixed #27032 -- Prevented setup_test_environment() from being called twice.

1 files changed, 7 insertions, 0 deletions

diff --git a/django/test/utils.py b/django/test/utils.py
index 3ae68b8a2f..57ae46fe1c 100644
--- a/django/test/utils.py
+++ b/django/test/utils.py
@@ -99,6 +99,13 @@ def setup_test_environment():
     Perform global pre-test setup, such as installing the instrumented template
     renderer and setting the email backend to the locmem email backend.
     """
+    if hasattr(Template, '_original_render'):
+        # Executing this function twice would overwrite the saved values.
+        raise RuntimeError(
+            "setup_test_environment() was already called and can't be called "
+            "again without first calling teardown_test_environment()."
+        )
+
     Template._original_render = Template._render
     Template._render = instrumented_test_render