Merge two streams.

lib/frappuccino/stream.rb

@@ -5,8 +5,12 @@ module Frappuccino
   class Stream
     include Observable
 
-    def initialize(source)
-      source.extend(Frappuccino::Source).add_observer(self)
+    def initialize(sources)
+      sources = Array(sources)
+
+      sources.each do |source|
+        source.extend(Frappuccino::Source).add_observer(self)
+      end
     end
 
     def update(event)
@@ -21,6 +25,10 @@ def map(&blk)
     def inject(start, &blk)
       Inject.new(self, start, &blk)
     end
+
+    def self.merge(stream_one, stream_two)
+      new([stream_one, stream_two])
+    end
   end
 
   private 

test/merge_test.rb

@@ -0,0 +1,21 @@
+require 'test_helper'
+
+describe "merging steams" do
+  it "produces one stream with both sets of events" do
+    button_one = Button.new
+    button_two = Button.new
+
+    stream_one = Frappuccino::Stream.new(button_one)
+    stream_two = Frappuccino::Stream.new(button_two)
+
+    merged_stream = Frappuccino::Stream.merge(stream_one, stream_two)
+    counter = merged_stream
+              .map {|event| event == :pushed ? 1 : 0 }
+              .inject(0) {|sum, n| sum + n }
+
+    button_one.push
+    button_two.push
+
+    assert_equal 2, counter.to_i
+  end
+end

test/mvp_test.rb

@@ -2,12 +2,6 @@
 
 require 'frappuccino'
 
-class Button
-  def push
-    emit(:pushed)
-  end
-end
-
 describe "MVP interaction" do
   it "can subscribe to an event stream" do
     button = Button.new

test/test_helper.rb

@@ -1 +1,8 @@
 require 'minitest/autorun'
+
+class Button
+  def push
+    emit(:pushed)
+  end
+end
+