On IE <= 10, Object.setPrototypeOf is impossible to shim.

Update test suite so that we don't test functions we can't provide.

README.md

@@ -64,7 +64,7 @@ details.
     * `keys()` (ES5)
     * `is()` ([a standalone shim is also available](https://github.com/ljharb/object-is))
     * `assign()`
-    * `setPrototypeOf()`
+    * `setPrototypeOf()` (IE >= 11)
 * `Math`:
     * `acosh()`
     * `asinh()`

es6-shim.js

@@ -841,7 +841,8 @@
 
     // Workaround bug in Opera 12 where setPrototypeOf(x, null) doesn't work,
     // but Object.create(null) does.
-    if (Object.getPrototypeOf(Object.setPrototypeOf({}, null)) !== null &&
+    if (Object.setPrototypeOf && Object.getPrototypeOf &&
+        Object.getPrototypeOf(Object.setPrototypeOf({}, null)) !== null &&
         Object.getPrototypeOf(Object.create(null)) === null) {
       (function() {
         var FAKENULL = Object.create(null);

test/collections.js

@@ -85,7 +85,7 @@ describe('Collections', function() {
 
     it('should be subclassable', function() {
       var MyMap = function() { Map.call(this, [['a','b']]); }
-      if (!MyMap.__proto__) { return; } // skip test if on IE < 11
+      if (!Object.setPrototypeOf) { return; } // skip test if on IE < 11
       Object.setPrototypeOf(MyMap, Map);
       MyMap.prototype = Object.create(Map.prototype, {
         constructor: { value: MyMap }
@@ -440,7 +440,7 @@ describe('Collections', function() {
 
     it('should be subclassable', function() {
       var MySet = function() { Set.call(this, ['a', 'b']); }
-      if (!MySet.__proto__) { return; } // skip test if on IE < 11
+      if (!Object.setPrototypeOf) { return; } // skip test if on IE < 11
       Object.setPrototypeOf(MySet, Set);
       MySet.prototype = Object.create(Set.prototype, {
         constructor: { value: MySet }

test/object.js

@@ -103,6 +103,10 @@ describe('Object', function() {
   });
 
   describe('Object.setPrototypeOf()', function() {
+    if (!Object.setPrototypeOf) {
+      return; // IE < 11
+    }
+
     describe('argument checking', function() {
       it('should throw TypeError if first arg is not object', function() {
         var nonObjects = [null, undefined, true, false, 1, 3, 'foo'];

test/promise/all.js

@@ -172,7 +172,7 @@ describe("Promise.all", function () {
         Promise.call(this, resolver);
       }
     };
-    if (!P.__proto__) { return done(); } // skip test if on IE < 11
+    if (!Object.setPrototypeOf) { return done(); } // skip test if on IE < 11
     Object.setPrototypeOf(P, Promise);
     P.prototype = Object.create(Promise.prototype, {
       constructor: { value: P }

test/promise/evil-promises.js

@@ -5,7 +5,7 @@ describe("Evil promises should not be able to break invariants", function () {
     // note that we have to create a trivial subclass, as otherwise the
     // Promise.resolve(evilPromise) is just the identity function.
     var EvilPromise = function(executor) { Promise.call(this, executor); };
-    if (!EvilPromise.__proto__) { return; } // skip test if on IE < 11
+    if (!Object.setPrototypeOf) { return done(); } // skip test if on IE < 11
     Object.setPrototypeOf(EvilPromise, Promise);
     EvilPromise.prototype = Object.create(Promise.prototype, {
       constructor: { value: EvilPromise }

test/promise/subclass.js

@@ -8,7 +8,7 @@ describe("Support user subclassing of Promise", function() {
       Promise.call(this, executor);
       this.mine = 'yeah';
     };
-    if (!MyPromise.__proto__) { return; } // skip test if on IE < 11
+    if (!Object.setPrototypeOf) { return done(); } // skip test if on IE < 11
     Object.setPrototypeOf(MyPromise, Promise);
     MyPromise.prototype = Object.create(Promise.prototype, {
       constructor: { value: MyPromise }