diff --git a/doc/data/messages/a/attribute-defined-outside-init/bad.py b/doc/data/messages/a/attribute-defined-outside-init/bad.py
new file mode 100644
index 0000000000..e62884d497
--- /dev/null
+++ b/doc/data/messages/a/attribute-defined-outside-init/bad.py
@@ -0,0 +1,3 @@
+class Student:
+    def register(self):
+        self.is_registered = True  # [attribute-defined-outside-init]
diff --git a/doc/data/messages/a/attribute-defined-outside-init/good.py b/doc/data/messages/a/attribute-defined-outside-init/good.py
new file mode 100644
index 0000000000..cc7d7acb18
--- /dev/null
+++ b/doc/data/messages/a/attribute-defined-outside-init/good.py
@@ -0,0 +1,6 @@
+class Student:
+    def __init__(self):
+        self.is_registered = False
+
+    def register(self):
+        self.is_registered = True