[Tests] skip Object.create tests when null objects are not available.

Also, “plain object” is not a term that exists outside this lib; so begin the move to the term “null object”.

Author: ljharb

README.md

@@ -39,11 +39,11 @@ assert.deepEqual(qs.parse('foo[bar]=baz'), {
 });
 ```
 
-When using the `plainObjects` option the parsed value is returned as a plain object, created via `Object.create(null)` and as such you should be aware that prototype methods will not exist on it and a user may set those names to whatever value they like:
+When using the `plainObjects` option the parsed value is returned as a null object, created via `Object.create(null)` and as such you should be aware that prototype methods will not exist on it and a user may set those names to whatever value they like:
 
 ```javascript
-var plainObject = qs.parse('a[hasOwnProperty]=b', { plainObjects: true });
-assert.deepEqual(plainObject, { a: { hasOwnProperty: 'b' } });
+var nullObject = qs.parse('a[hasOwnProperty]=b', { plainObjects: true });
+assert.deepEqual(nullObject, { a: { hasOwnProperty: 'b' } });
 ```
 
 By default parameters that would overwrite properties on the object prototype are ignored, if you wish to keep the data from those fields either use `plainObjects` as mentioned above, or set `allowPrototypes` to `true` which will allow user input to overwrite those properties. *WARNING* It is generally a bad idea to enable this option as it can cause problems when attempting to use the properties that have been overwritten. Always be careful with this option.

test/parse.js

@@ -379,7 +379,7 @@ test('parse()', function (t) {
         st.end();
     });
 
-    t.test('parses plain objects correctly', function (st) {
+    t.test('parses null objects correctly', { skip: !Object.create }, function (st) {
         var a = Object.create(null);
         a.b = 'c';
 
@@ -408,7 +408,7 @@ test('parse()', function (t) {
         st.end();
     });
 
-    t.test('can return plain objects', function (st) {
+    t.test('can return null objects', { skip: !Object.create }, function (st) {
         var expected = Object.create(null);
         expected.a = Object.create(null);
         expected.a.b = 'c';

test/stringify.js

@@ -126,7 +126,7 @@ test('stringify()', function (t) {
         st.end();
     });
 
-    t.test('stringifies an empty object', function (st) {
+    t.test('stringifies a null object', { skip: !Object.create }, function (st) {
         var obj = Object.create(null);
         obj.a = 'b';
         st.equal(qs.stringify(obj), 'a=b');
@@ -141,10 +141,8 @@ test('stringify()', function (t) {
         st.end();
     });
 
-    t.test('stringifies an object with an empty object as a child', function (st) {
-        var obj = {
-            a: Object.create(null)
-        };
+    t.test('stringifies an object with a null object as a child', { skip: !Object.create }, function (st) {
+        var obj = { a: Object.create(null) };
 
         obj.a.b = 'c';
         st.equal(qs.stringify(obj), 'a%5Bb%5D=c');