(new) added assert.isNull, and made isObject more robust

Author: cloudhead

lib/vows/macros.js

@@ -74,6 +74,11 @@ assert.isNaN = function (actual, message) {
         assert.fail(actual, 'NaN', message || "expected {actual} to be NaN", "isNaN", assert.isNaN);
     }
 };
+assert.isNull = function (actual, message) {
+    if (actual !== null) {
+        assert.fail(actual, 'null', message || "expected {actual} to be null", "===", assert.isNull);
+    }
+};
 assert.isString = function (actual, message) {
     assertTypeOf(actual, 'string', message || "expected {actual} to be a String", assert.isString);
 };
@@ -102,7 +107,7 @@ function isString (obj) {
 }
 
 function isObject (obj) {
-    return typeof(obj) === 'object' && obj instanceof Object && !isArray(obj);
+    return typeof(obj) === 'object' && obj && !isArray(obj);
 }
 
 // A better `typeof`