Move /src/test to /tests

tests/rustdoc-json/return_private.rs

@@ -0,0 +1,15 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/96161>.
+// ignore-tidy-linelength
+
+#![feature(no_core)]
+#![no_core]
+
+mod secret {
+    pub struct Secret;
+}
+
+// @is "$.index[*][?(@.name=='get_secret')].kind" \"function\"
+// @is "$.index[*][?(@.name=='get_secret')].inner.decl.output.inner.name" \"secret::Secret\"
+pub fn get_secret() -> secret::Secret {
+    secret::Secret
+}