DB & Dev Tools · APIs: a drop inside a folder lands last, tested

The collection's unit test now drops a request into a folder that holds
two, and asserts it lands after them.

src/devtools/collection.rs

@@ -239,6 +239,11 @@ mod tests {
             keys(&moved(&items, "x", "b", DropAt::Inside)),
             ["a[y]", "b[x]", "z"]
         );
+        assert_eq!(
+            keys(&moved(&items, "z", "a", DropAt::Inside)),
+            ["a[x,y,z]", "b[]"],
+            "a drop inside a folder lands last"
+        );
         assert_eq!(
             keys(&moved(&items, "z", "x", DropAt::Before)),
             ["a[z,x,y]", "b[]"]