feat(formatters): add console duration formatter

specs/support/fixtures/formatters/duration.txt

@@ -0,0 +1,3 @@
+  Specs loaded in 0.002s
+  Finished in 0.004s
+

specs/units/formatters/console/duration_formatter.spec.coffee

@@ -0,0 +1,25 @@
+DurationFormatter = spectacular.formatters.console.DurationFormatter
+
+describe DurationFormatter, ->
+  fixture 'formatters/duration.txt', as: 'expected'
+
+  given 'options', ->
+    {
+      colors: false
+    }
+
+  given 'runner', ->
+    {
+      options: @options
+      loadStartedAt: { getTime: -> 0 }
+      loadEndedAt: { getTime: -> 2 }
+      specsStartedAt: { getTime: -> 0 }
+      specsEndedAt: { getTime: -> 4 }
+    }
+
+  given 'formatter', -> new DurationFormatter @runner
+
+  subject -> @formatter.format()
+
+  itBehavesLike 'a formatter'
+

src/formatters/console.coffee

@@ -11,6 +11,33 @@ class spectacular.formatters.console.SeedFormatter
     promise.resolve "  Seed #{spectacular.utils.colorize @seed.toString(), 'cyan', @options.colors}\n\n"
 
     promise
+
+class spectacular.formatters.console.DurationFormatter
+  constructor: (@runner) ->
+    {@options} = @runner
+
+  format: ->
+    promise = new spectacular.Promise
+
+    {loadStartedAt, loadEndedAt, specsStartedAt, specsEndedAt} = @runner
+
+    if loadStartedAt? and loadEndedAt?
+      loadDuration = @formatDuration loadStartedAt, loadEndedAt
+
+    specsDuration = @formatDuration specsStartedAt, specsEndedAt
+
+    res = ''
+    res += "  Specs loaded in #{loadDuration}\n" if loadDuration?
+    res += "  Finished in #{specsDuration}\n\n"
+
+    promise.resolve res
+
+    promise
+
+  formatDuration: (start, end) ->
+    duration = (end.getTime() - start.getTime()) / 1000
+    spectacular.utils.colorize "#{Math.max 0, duration}s", 'yellow', @options.colors
+
 class spectacular.formatters.console.ErrorStackFormatter
   constructor: (@stack, @options) ->
     @parser = new spectacular.errors.ErrorParser @stack