src/third_party/mozjs-45/js/src/jit-test/tests/collections/Map-set-returns-this.js

// Bug 1031632 - Map.prototype.set, WeakMap.prototype.set and
// Set.prototype.add should be chainable

var m = new Map();
assertEq(m.set('oof', 'RAB'), m);
var a = m.set('foo', 'BAR').get('foo');
assertEq(a, 'BAR');