introduce isAsyncFunction and isNotAsyncFunction assertions

Author: koddsson

lib/chai/interface/assert.js

@@ -590,6 +590,42 @@ assert.isNotFunction = function (val, msg) {
   new Assertion(val, msg, assert.isNotFunction, true).to.not.be.a('function');
 };
 
+/**
+ * ### .isAsyncFunction(value, [message])
+ *
+ * Asserts that `value` is a async function.
+ *
+ *     async function serveTea() { return 'cup of tea'; };
+ *     assert.isAsyncFunction(serveTea, 'great, we can have tea now');
+ *
+ * @name isAsyncFunction
+ * @param {Mixed} value
+ * @param {String} message
+ * @namespace Assert
+ * @api public
+ */
+assert.isAsyncFunction = function (val, msg) {
+  new Assertion(val, msg, assert.isAsyncFunction, true).to.be.a('asyncfunction');
+};
+
+/**
+ * ### .isNotAsyncFunction(value, [message])
+ *
+ * Asserts that `value` is _not_ a async function.
+ *
+ *     var serveTea = [ 'heat', 'pour', 'sip' ];
+ *     assert.isNotAsyncFunction(serveTea, 'great, we have listed the steps');
+ *
+ * @name isNotAsyncFunction
+ * @param {Mixed} value
+ * @param {String} message
+ * @namespace Assert
+ * @api public
+ */
+assert.isNotAsyncFunction = function (val, msg) {
+  new Assertion(val, msg, assert.isNotAsyncFunction, true).to.not.be.a('asyncfunction');
+};
+
 /**
  * ### .isObject(value, [message])
  *

test/assert.js

@@ -524,9 +524,6 @@ describe('assert', function () {
   it('isFunction', function() {
     var func = function() {};
     assert.isFunction(func);
-   
-    async function asyncFunction() {};
-    assert.isFunction(asyncFunction);
 
     err(function () {
       assert.isFunction({}, 'blah');
@@ -540,6 +537,23 @@ describe('assert', function () {
       assert.isNotFunction(function () {}, 'blah');
     }, "blah: expected [Function] not to be a function");
   });
+  
+  it('isAsyncFunction', function() {
+    async function func() {};
+    assert.isAsyncFunction(func);
+
+    err(function () {
+      assert.isAsyncFunction(function () {}, 'blah');
+    }, "blah: expected [Function] to be an asyncfunction");
+  });
+
+  it('isNotAsyncFunction', function () {
+    assert.isNotAsyncFunction(5);
+
+    err(function () {
+      assert.isNotAsyncFunction(async function () {}, 'blah');
+    }, "blah: expected [Function] not to be an asyncfunction");
+  });
 
   it('isArray', function() {
     assert.isArray([]);