Move /src/test to /tests

tests/ui/hashmap/hashmap-capacity-overflow.rs

@@ -0,0 +1,12 @@
+// run-fail
+// error-pattern:capacity overflow
+// ignore-emscripten no processes
+
+use std::collections::hash_map::HashMap;
+use std::mem::size_of;
+
+fn main() {
+    let threshold = usize::MAX / size_of::<(u64, u64, u64)>();
+    let mut h = HashMap::<u64, u64>::with_capacity(threshold + 100);
+    h.insert(0, 0);
+}