1 files changed, 8 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/collections/Map-constructor-duplicates.js b/js/src/jit-test/tests/collections/Map-constructor-duplicates.js
new file mode 100644
index 0000000000..125081bf87
--- /dev/null
+++ b/js/src/jit-test/tests/collections/Map-constructor-duplicates.js
@@ -0,0 +1,8 @@
+// When the argument to Map contains a key multiple times, the last value is retained.
+
+var arg = [["zero", 7], ["one", 1], ["two", 4], ["zero", 8], ["two", 2], ["zero", 0]];
+var m = new Map(arg);
+assertEq(m.get("zero"), 0);
+assertEq(m.get("one"), 1);
+assertEq(m.get("two"), 2);
+assertEq(m.size, 3);