Implement isIterable

Author: koddsson

lib/chai/interface/assert.js

@@ -2484,6 +2484,23 @@ assert.oneOf = function (inList, list, msg) {
   new Assertion(inList, msg, assert.oneOf, true).to.be.oneOf(list);
 }
 
+/**
+ * ### isIterable(obj, [message])
+ *
+ * Asserts that the target is an iterable, which means that it has a iterator
+ * with the exception of `String.`
+ *
+ *     assert.isIterable([1, 2]);
+ *
+ * @param {unknown} obj
+ * @param {string} [msg]
+ * @namespace Assert
+ * @api public
+ */
+assert.isIterable = function(obj, msg) {
+  new Assertion(obj, msg, assert.isIterable, true).to.be.an('iterable');
+}
+
 /**
  * ### .changes(function, object, property, [message])
  *

test/assert.js

@@ -2377,6 +2377,36 @@ describe('assert', function () {
     }, 'blah: the argument to most must be a number');
   });
 
+  it('iterable', function() {
+    assert.isIterable([1, 2, 3]);
+    assert.isIterable(new Map([[1, 'one'], [2, 'two'], [3, 'three']]));
+    assert.isIterable(new Set([1, 2, 3]));
+
+    err(function() {
+      assert.isIterable(42);
+    }, 'expected 42 to be an iterable');
+
+    err(function() {
+      assert.isIterable('hello');
+    }, "expected 'hello' to be an iterable");
+
+    err(function() {
+      assert.isIterable(undefined);
+    }, 'expected undefined to be an iterable'); 
+
+    err(function() {
+      assert.isIterable(null);
+    }, 'expected null to be an iterable');
+
+    err(function() {
+      assert.isIterable(true);
+    }, 'expected true to be an iterable');
+
+    err(function() {
+      assert.isIterable({ key: 'value' });
+    }, 'expected { key: \'value\' } to be an iterable');
+  });
+
   it('change', function() {
     var obj = { value: 10, str: 'foo' },
         heroes = ['spiderman', 'superman'],