diff --git a/lib/assert.js b/lib/assert.js
index 09f588d16..0e99d4509 100644
--- a/lib/assert.js
+++ b/lib/assert.js
@@ -352,3 +352,182 @@ assert.doesNotThrow = function(block, /*optional*/error, /*optional*/message) {
 };
 
 assert.ifError = function (err) { if (err) {throw err;}};
+
+// The following asserts are the extended assert functions from
+// Christian Johansen's Test-Driven Javascript Development book.
+
+assert.isNull = function (value, message) {
+    if (value !== null) {
+        assert.fail(value, null, message, "===", assert.isNull);
+    }
+}
+
+assert.isNotNull = function (value, message) {
+    if (value === null) {
+        assert.fail(value, null, message, "!==", assert.isNotNull);
+    }
+}
+
+function typeOf (value, type, message, stackStart) {
+    if (typeof value != type) {
+        assert.fail(value, type, message, "typeof", stackStart);
+    }
+}
+
+function notTypeOf (value, type, message, stackStart) {
+    if (typeof value == type) {
+        assert.fail(value, type, message, "!typeof", stackStart);
+    }
+}
+
+assert.isTypeOf = function (value, type, message) {
+    typeOf(value, type, message, assert.isTypeOf);
+};
+
+assert.isNotTypeOf = function (value, type, message) {
+    notTypeOf(value, type, message, assert.isNotTypeOf);
+};
+
+assert.isObject = function (value, message) {
+    typeOf(value, "object", message, assert.isObject);
+};
+
+assert.isFunction = function (value, message) {
+    typeOf(value, "function", message, assert.isFunction);
+};
+
+assert.isString = function (value, message) {
+    typeOf(value, "string", message, assert.isString);
+};
+
+assert.isBoolean = function (value, message) {
+    typeOf(value, "boolean", message, assert.isBoolean);
+};
+
+assert.isNumber = function (value, message) {
+    typeOf(value, "number", message, assert.isNumber);
+};
+
+assert.isUndefined = function (value, message) {
+    typeOf(value, "undefined", message, assert.isUndefined);
+};
+
+assert.isNotUndefined = function (value, message) {
+    notTypeOf(value, "undefined", message, assert.isNotUndefined);
+};
+
+assert.isArray = function (value, message) {
+    if (Object.prototype.toString.call(value) != "[object Array]") {
+        assert.fail(value, "Array", message, "[[Class]]", assert.isArray);
+    }
+};
+
+assert.isBuffer = function (value, message) {
+    if (!Buffer.isBuffer(value)) {
+        assert.fail(value, "Buffer", message, "isBuffer", assert.isBuffer);
+    }
+};
+
+assert.isNaN = function (value, message) {
+    if (!isNaN(value)) {
+        assert.fail(value, "NaN", message, "==", assert.isNaN);
+    }
+}
+
+assert.isNotNaN = function (value, message) {
+    if (isNaN(value)) {
+        assert.fail(value, "NaN", message, "!=", assert.isNotNaN);
+    }
+}
+
+assert.match = function (value, pattern, message) {
+    if (!pattern.test(value)) {
+        assert.fail(value, pattern, message, "test", assert.match);
+    }
+}
+
+assert.noMatch = function (value, pattern, message) {
+    if (pattern.test(value)) {
+        assert.fail(value, pattern, message, "!test", assert.noMatch);
+    }
+}
+
+function inherits (ancestor, object) {
+    if (typeof object == "function") {
+        return object.prototype.isPrototypeOf(ancestor);
+    }
+
+    return object.isPrototypeOf(ancestor);
+}
+
+assert.inherits = function (ancestor, object, message) {
+    if (!inherits(ancestor, object)) {
+        assert.fail(ancestor, object, message, "inherits", assert.inherits);
+    }
+}
+
+assert.doesNotInherit = function (ancestor, object, message) {
+    if (inherits(ancestor, object)) {
+        assert.fail(ancestor, object, message, "!inherits", assert.doesNotInherit);
+    }
+}
+
+assert.isPrototypeOf = function (proto, object, message) {
+    if (!proto.isPrototypeOf(object)) {
+        assert.fail(proto, object, message, "isPrototypeOf", assert.isPrototypeOf);
+    }
+}
+
+assert.isNotPrototypeOf = function (proto, object, message) {
+    if (proto.isPrototypeOf(object)) {
+        assert.fail(proto, object, message, "!isPrototypeOf", assert.isNotPrototypeOf);
+    }
+}
+
+assert.isWritable = function (object, property, message) {
+    var descriptor = Object.getOwnPropertyDescriptor(object, property);
+
+    if (!descriptor.writable) {
+        assert.fail(object, property, message, "isWritable", assert.isWritable);
+    }
+}
+
+assert.isNotWritable = function (object, property, message) {
+    var descriptor = Object.getOwnPropertyDescriptor(object, property);
+
+    if (descriptor.writable) {
+        assert.fail(object, property, message, "isNotWritable", assert.isNotWritable);
+    }
+}
+
+assert.isConfigurable = function (object, property, message) {
+    var descriptor = Object.getOwnPropertyDescriptor(object, property);
+
+    if (!descriptor.configurable) {
+        assert.fail(object, property, message, "isConfigurable", assert.isConfigurable);
+    }
+}
+
+assert.isNotConfigurable = function (object, property, message) {
+    var descriptor = Object.getOwnPropertyDescriptor(object, property);
+
+    if (descriptor.configurable) {
+        assert.fail(object, property, message, "isNotConfigurable", assert.isNotConfigurable);
+    }
+}
+
+assert.isEnumerable = function (object, property, message) {
+    var descriptor = Object.getOwnPropertyDescriptor(object, property);
+
+    if (!descriptor.enumerable) {
+        assert.fail(object, property, message, "isEnumerable", assert.isEnumerable);
+    }
+}
+
+assert.isNotEnumerable = function (object, property, message) {
+    var descriptor = Object.getOwnPropertyDescriptor(object, property);
+
+    if (descriptor.enumerable) {
+        assert.fail(object, property, message, "isNotEnumerable", assert.isNotEnumerable);
+    }
+}