Add length() sugar method to lists

docs/list.md

@@ -31,6 +31,7 @@ This list of words can abstracted and interacted with via a `List` with ease. He
     * [ItemSelector](#itemselector)
     * [ItemClass](#itemclass)
     * [Items](#items)
+    * [Length](#length)
     * [Filter](#filter)
     * [Map](#map)
     * [Each](#each)
@@ -55,6 +56,16 @@ The `Widget` to be instantiated and used when interacting with each item in the
 
 Returns a `Promise` that resolves to a list of `Widgets` present in the `DOM` at call time.
 
+## Length
+
+`function length()...`
+
+Returns a `Promise` that resolves to the length of the list.
+
+```js
+new ListItems().length().should.eventually.eql(5)
+```
+
 ## Filter
 
 `function filter(<predicateMethod>(itemInstance))...`

src/widgets/Widget.List.coffee

@@ -30,6 +30,9 @@ class @Widget.List extends @Widget
   each: (iter) ->
     @map.apply(this, arguments).then -> @items
 
+  length: ->
+    @items().then (items) -> items.length
+
   invoke: (opts) ->
     if(_.isString(opts) or _.isFunction(opts))
       opts = {method: opts}

test/integration/features/list.feature

@@ -27,6 +27,9 @@ Feature: Manipulating Lists
   Scenario: Calling AT with a string
     When I call at with a string I should get an error
 
+  Scenario: Getting length of a list
+    When I call length I should receive 5
+
   Scenario: Nested list lookup
     When I find the "span" within ".nested" I should see 3 items
 

test/integration/steps/list_steps.coffee

@@ -33,6 +33,10 @@ module.exports = ->
     .then (item) -> item.getHtml()
     .should.eventually.eql(content)
 
+  @When /^I call length I should receive (\d+)$/, (expectedLength) ->
+    new @Widgets.List().length()
+    .should.eventually.eql(+expectedLength)
+
   @When /^I call at with a string I should get an error$/, ->
     expect( =>
       new @Widgets.List().at("0")