Add GUI test for auto-hide-trait-implementations setting

src/test/rustdoc-gui/auto-hide-trait-implementations.goml

@@ -0,0 +1,13 @@
+// Checks that the setting "auto hide trait implementations" is working as expected.
+goto: file://|DOC_PATH|/test_docs/struct.Foo.html
+
+// By default, the trait implementations are not collapsed.
+assert-attribute: ("#trait-implementations-list > details", {"open": ""}, ALL)
+
+// We now set the setting to auto hide all trait implementations.
+local-storage: {"rustdoc-auto-hide-trait-implementations": "true" }
+// We reload to ensure the trait implementations are collapsed as expected.
+reload:
+
+// We now check that all matching elements don't have the open attributes.
+assert-attribute-false: ("#trait-implementations-list > details", {"open": ""}, ALL)

src/test/rustdoc-gui/src/test_docs/lib.rs

@@ -5,6 +5,7 @@
 #![feature(doc_keyword)]
 #![feature(doc_cfg)]
 
+use std::convert::AsRef;
 use std::fmt;
 
 /// Basic function with some code examples:
@@ -36,6 +37,12 @@ impl Foo {
     }
 }
 
+impl AsRef<str> for Foo {
+    fn as_ref(&self) -> &str {
+        "hello"
+    }
+}
+
 /// Just a normal enum.
 #[doc(alias = "ThisIsAnAlias")]
 pub enum WhoLetTheDogOut {