Oh look! Unit tests found a bug! I was calling image.last.width inste…

…ad of image.first.height for the height of the diff :(

lib/compatriot/image_differ.rb

@@ -4,19 +4,17 @@
 module Compatriot
   class ImageDiffer
 
-    def self.diff(results)
+    def self.diff(results, strategy = :color_difference)
       images = results.map{|r| ChunkyPNG::Image.from_file(r) }
-      f = self.color_difference(images, results.first)
-      File.join(
-        File.basename(File.dirname(f)),
-        File.basename(f)
-      )
+      self.send(strategy, images, results.first)
     end
 
     def self.same_pixels_exactly(images, name)
-      output = ChunkyPNG::Image.new(images.first.width, images.last.width, WHITE)
+      output = ChunkyPNG::Image.new(images.first.width, images.first.height, WHITE)
       diff = []
 
+      # each_pixel(images.first, images.last) do |x, y|
+
       images.first.height.times do |y|
         images.first.row(y).each_with_index do |pixel, x|
           output[x,y] = pixel
@@ -33,11 +31,14 @@ def self.same_pixels_exactly(images, name)
       output.rect(x.min, y.min, x.max, y.max, ChunkyPNG::Color.rgb(0,255,0))
       filename = "#{name}-same_exactly.png"
       output.save(filename)
-      filename
+      File.join(
+        File.basename(File.dirname(filename)),
+        File.basename(filename)
+      )
     end
 
     def self.color_difference(images, name)
-      output = ChunkyPNG::Image.new(images.first.width, images.last.width, WHITE)
+      output = ChunkyPNG::Image.new(images.first.width, images.first.height, WHITE)
       diff = []
 
       images.first.height.times do |y|
@@ -61,7 +62,10 @@ def self.color_difference(images, name)
 
       filename = "#{name}-color_difference.png"
       output.save(filename)
-      filename
+      File.join(
+        File.basename(File.dirname(filename)),
+        File.basename(filename)
+      )
     end
   end
 end

spec/unit/image_differ_spec.rb

@@ -0,0 +1,32 @@
+require_relative '../spec_helper'
+
+describe Compatriot::ImageDiffer do
+  describe "self#diff" do
+    it "calls chunky_png on each image path" do
+      file_one = stub
+      file_two = stub
+
+      ChunkyPNG::Image.expects(:from_file).with(file_one)
+      ChunkyPNG::Image.expects(:from_file).with(file_two)
+      Compatriot::ImageDiffer.stubs(:color_difference)
+
+      Compatriot::ImageDiffer.diff([file_one, file_two])
+    end
+
+    it "returns the filename of the diff" do
+    end
+
+    it "uses the strategy passed in" do
+    end
+  end
+
+  describe "self#color_difference" do
+    it "starts a new white image with the same dimensions" do
+      ChunkyPNG::Image.expects(:new).with(1, 2, ChunkyPNG::Image::WHITE)
+
+      image1 = stub(:width => 1, :height => 2)
+
+      Compatriot::ImageDiffer.color_difference([image1], stub)
+    end
+  end
+end