[Tests] use has-strict-mode

Author: ljharb

package.json

@@ -44,6 +44,7 @@
 		"define-properties": "^1.2.1",
 		"function-bind": "^1.1.2",
 		"functions-have-names": "^1.2.3",
+		"has-strict-mode": "^1.0.1",
 		"istanbul": "^0.4.5",
 		"tape": "^5.9.0"
 	}

tests/tests.js

@@ -1,5 +1,7 @@
 'use strict';
 
+var supportsStrictMode = require('has-strict-mode')();
+
 module.exports = function (codePointAt, t) {	
 	t.test('String that starts with a BMP symbol', function (st) {
 		st.equal(codePointAt('abc\uD834\uDF06def', -1), undefined);
@@ -82,8 +84,6 @@ module.exports = function (codePointAt, t) {
 		st.end();
 	});
 
-	var supportsStrictMode = (function () { return typeof this === 'undefined'; }());
-
 	t.test('bad string/this value', { skip: !supportsStrictMode }, function (st) {
 		st['throws'](function () { return codePointAt(undefined, 'a'); }, TypeError, 'undefined is not an object');
 		st['throws'](function () { return codePointAt(null, 'a'); }, TypeError, 'null is not an object');