diff --git a/tests/ui/mixed_attributes_style.rs b/tests/ui/mixed_attributes_style.rs
index 4f89aa8a5e55..9f39949110cf 100644
--- a/tests/ui/mixed_attributes_style.rs
+++ b/tests/ui/mixed_attributes_style.rs
@@ -38,3 +38,18 @@ mod bar {
 fn main() {
     // test code goes here
 }
+
+// issue #12435
+#[cfg(test)]
+mod tests {
+    //! Module doc, don't lint
+}
+#[allow(unused)]
+mod baz {
+    //! Module doc, don't lint
+    const FOO: u8 = 0;
+}
+/// Module doc, don't lint
+mod quz {
+    #![allow(unused)]
+}
diff --git a/tests/ui/mixed_attributes_style.stderr b/tests/ui/mixed_attributes_style.stderr
index ed798073cb7c..02b19cc98468 100644
--- a/tests/ui/mixed_attributes_style.stderr
+++ b/tests/ui/mixed_attributes_style.stderr
@@ -26,5 +26,29 @@ LL | | mod bar {
 LL | |     #![allow(unused)]
    | |_____________________^
 
-error: aborting due to 3 previous errors
+error: item has both inner and outer attributes
+  --> tests/ui/mixed_attributes_style.rs:43:1
+   |
+LL | / #[cfg(test)]
+LL | | mod tests {
+LL | |     //! Module doc, don't lint
+   | |______________________________^
+
+error: item has both inner and outer attributes
+  --> tests/ui/mixed_attributes_style.rs:47:1
+   |
+LL | / #[allow(unused)]
+LL | | mod baz {
+LL | |     //! Module doc, don't lint
+   | |______________________________^
+
+error: item has both inner and outer attributes
+  --> tests/ui/mixed_attributes_style.rs:52:1
+   |
+LL | / /// Module doc, don't lint
+LL | | mod quz {
+LL | |     #![allow(unused)]
+   | |_____________________^
+
+error: aborting due to 6 previous errors